Pfizer, a Delaware corporation, is a research-based, global pharmaceutical company that discovers, develops, manufactures and markets leading prescription medicines for humans and animals. Pfizer operates in two business segments: pharmaceutical and animal health. Pfizer also operates several other businesses, including the manufacture of gelatin capsules, contract manufacturing and bulk pharmaceutical chemicals. Pfizer.s pharmaceutical business is the largest pharmaceutical business in the world. Each year, Pfizer's pharmaceuticals help over 100 million people throughout the world live longer, healthier lives. With medicines across 11 therapeutic areas, Pfizer helps to treat and prevent many of the most common and most challenging conditions of recent time. Pfizer's products are in Cardiovascular and Metabolic Diseases, Central Nervous System Disorders, Arthritis and Pain, Infectious and Respiratory Diseases, Urology, Oncology, Ophthalmology, Erectile Dysfunction and Endocrine Disorders.
Pfizer's common stock (NYSE: PFE) is listed on the NYSE. Pfizer is a member of the S&P 500 and the Fortune 500. The principal executive offices of Pfizer are located at 235 East 42nd Street, New York, New York, 10017-5755, and its telephone number is 1-212-573-2323.

Wagner Acquisition Corp., sometimes referred to in this proxy statement/prospectus as Merger Sub, a direct wholly-owned subsidiary of Pfizer, was formed solely for the purpose of consummating the merger. Wagner Acquisition Corp. has not carried on any activities to date, except for activities incidental to its formation and activities undertaken in connection with the transactions contemplated by the merger agreement. The principal executive offices of Wagner Acquisition Corp. are located at 235 East 42nd Street, New York, New York, 10017-5755, and its telephone number is 1-212-573-2323.

Wyeth, a Delaware corporation, organized in 1926, is currently engaged in the discovery, development, manufacture, distribution and sale of a diversified line of products in three primary businesses: Wyeth Pharmaceuticals, Wyeth Consumer Healthcare, and Fort Dodge Animal Health. Wyeth Pharmaceuticals includes branded human ethical pharmaceuticals, biotechnology products, vaccines and nutritional products. Wyeth Pharmaceuticals products include neuroscience therapies, musculoskeletal therapies, vaccines, nutritional products, anti-infectives, women.s health care products, hemophilia treatments, gastroenterology drugs, immunological products and oncology therapies. Wyeth Consumer Healthcare products include pain management therapies, including analgesics and heat wraps, cough/cold/allergy remedies, nutritional supplements, and hemorrhoidal care and personal care items sold over-the-counter. Fort Dodge Animal Health products include vaccines, pharmaceuticals, parasite control and growth implants.
Wyeth's common stock (NYSE: WYE) and Wyeth.s $2 Convertible Preferred Stock (NYSE: WYEPR) are listed on the NYSE. Wyeth is a member of the S&P 500 and Fortune 500. The principal executive offices of Wyeth are located at Five Giralda Farms, Madison, New Jersey 07940, and its telephone number is 1-973-660-5000.

Pfizer, Wyeth and Merger Sub entered into the Agreement and Plan of Merger, dated as of January 25, 2009, which, as it may be amended from time to time, is referred to in this proxy statement/prospectus as the merger agreement. Subject to the terms and conditions of the merger agreement, Merger Sub will be merged with and into Wyeth, with Wyeth continuing as the surviving corporation. Upon the completion of the merger, Wyeth will be a wholly-owned subsidiary of Pfizer, and Wyeth common stock and Wyeth $2 Convertible Preferred Stock will no longer be outstanding or publicly traded.

If the merger is completed, you will have the right to receive, subject to adjustment under limited circumstances, in exchange for each share of Wyeth common stock you own immediately prior to the effective time of the merger, a combination of $33.00 in cash, without interest, and 0.985 of a share of Pfizer common stock (which is sometimes referred to in this proxy statement/prospectus as the exchange ratio), which together are sometimes referred to in this proxy statement/prospectus as the merger consideration. Pfizer will not issue any fractional shares of Pfizer common stock in the merger. Wyeth stockholders who would otherwise be entitled to a fractional share of Pfizer common stock will instead receive an amount in cash based on the volume weighted average price of Pfizer common stock for the five consecutive trading days ending two days prior to the effective time of the merger, as such prices are reported on the NYSE Transaction Reporting System.

Other than possible adjustments described in the next paragraph below, the exchange ratio of 0.985 of a share of Pfizer common stock is fixed, which means that it will not change between now and the date of the merger, including as a result of a change in the trading price of Pfizer common stock or Wyeth common stock. Therefore, the value of the shares of Pfizer common stock received by Wyeth stockholders in the merger will depend on the market price of Pfizer common stock at the time the merger is completed.

The exchange ratio will be adjusted if the exchange ratio would result in Pfizer issuing in excess of 19.9% of its outstanding common stock as a result of the merger. In such circumstance, the exchange ratio will be reduced to the minimum extent necessary so that the number of shares of Pfizer common stock issued or issuable as a result of the merger will equal no more than 19.9% of its outstanding common stock and the cash portion of the merger consideration will be increased by an equivalent value (based on the volume weighted average price of Pfizer common stock for the five consecutive trading days ending two days prior to the effective time of the merger, as such prices are reported on the NYSE Transaction Reporting System).

At the time of the execution of the merger agreement, the number of shares of Pfizer common stock (and securities convertible or exercisable for Pfizer common stock) expected to be issued in the merger constituted less than 19.9% of Pfizer.s outstanding shares of common stock, and Pfizer and Wyeth currently do not anticipate that any adjustment to the exchange ratio will be required. A vote by Wyeth stockholders for the adoption of the merger agreement constitutes approval of the merger whether or not the exchange ratio and cash portion are adjusted as described above.

Upon completion of the merger, each share of Wyeth $2 Convertible Preferred Stock issued and outstanding immediately prior to completion of the merger will be converted into the right to receive one share of a new series of Pfizer preferred stock having the same powers, designations, preferences and rights (to the fullest extent practicable) as the shares of the Wyeth $2 Convertible Preferred Stock. We refer to this new series of Pfizer preferred stock in this proxy statement/prospectus as the Pfizer $2 Convertible Preferred Stock. However, on April 23, 2009, Wyeth announced that, pursuant to a request from Pfizer made in accordance with the terms and conditions of the merger agreement, Wyeth will redeem all of its outstanding Wyeth $2 Convertible Preferred Stock, effective on July 15, 2009. Therefore, it is expected that there will not be any shares of Wyeth $2 Convertible Preferred Stock outstanding at the effective time of the merger. In such case, Pfizer will not create or issue a new series of preferred stock in connection with the merger.

Each outstanding option to acquire Wyeth common stock granted under Wyeth.s stock incentive plans, which is referred to in this proxy statement/prospectus as a Wyeth stock option, whether or not then vested and exercisable, will become fully vested and exercisable immediately prior to, and then will be canceled at, the effective time of the merger, and the holder of such option will be entitled to receive as soon as practicable after the effective time of the merger but in no event later than ten business days following the effective time of the merger an amount in cash, without interest and less any applicable tax to be withheld, equal to (i) the excess, if any, of the per share value of the merger consideration to be received by holders of Wyeth common stock in the merger over the per share exercise price of such Wyeth stock option multiplied by (ii) the total number of shares of Wyeth common stock underlying such Wyeth stock option, with the aggregate amount of such payment rounded up to the nearest cent. The .per share value of the merger consideration. is equal to the sum of (x) the cash portion of the merger consideration, plus (y) the market value of the stock portion of the merger consideration (determined based on the volume weighted average of the price of Pfizer common stock for the five consecutive trading days ending two days prior to the effective time of the merger, as such prices are reported on the NYSE Transaction Reporting System). If the per share exercise price of any Wyeth stock option is equal to or greater than the per share value of the merger consideration, then the stock option will be canceled without any payment to the stock option holder.

Also at the effective time of the merger, each outstanding share of restricted stock, each outstanding deferred stock unit award (which is referred to in this proxy statement/prospectus as a DSU) and each outstanding restricted stock unit award (which is referred to in this proxy statement/prospectus as a RSU), including each outstanding performance share unit award (but excluding certain RSUs that constitute deferred compensation, as discussed below), will become fully vested and then will be canceled and the holder of such vested awards will be entitled to receive an amount in cash, without interest and less any applicable tax to be withheld, equal to the per share value of the merger consideration in respect of each share of Wyeth common stock into which the vested portion of such outstanding restricted stock, DSU and RSU, as applicable, would otherwise be convertible (except that with respect to any performance share unit award which by the terms of the award agreement pursuant to which it was granted provides for a lesser percentage of such performance share unit award to become vested upon the effective time of the merger, such performance share unit award will only become vested as to such lesser percentage (with the remaining unvested portion being canceled without payment)). These cash amounts will be paid out as soon as practicable after the effective time of the merger but in no event later than ten business days following the effective time of the merger.

Also at the effective time of the merger, each outstanding RSU that constitutes deferred compensation under Section 409A of the Internal Revenue Code of 1986, as amended (which is referred to in this proxy statement/prospectus as the .Internal Revenue Code.), and that cannot be immediately settled at closing due to tax law restrictions, which units will be referred to in this proxy statement/prospectus as 409A RSUs, will, as of the effective time of the merger, become a vested right to receive the merger consideration in respect of each share of Wyeth common stock into which such 409A RSU would otherwise be convertible. Such merger consideration will be deposited into a grantor trust in which the cash portion of the merger consideration will accrue interest at a designated market rate and the portion of the merger consideration that is Pfizer common stock will accrue dividends in the form of additional shares of Pfizer common stock in the same amount and at the same time as dividends are paid on Pfizer common stock, and all of these amounts, less any applicable tax to be withheld, will be paid out in accordance with the applicable payment schedules provided for under the applicable stock incentive plan, award agreement and/or deferral elections (which are, collectively, referred to in this proxy statement/prospectus as deferred payment terms) made by the holders of such 409A RSUs.

Also at the effective time of the merger, each phantom share of Wyeth common stock credited to any non-employee director.s account under the Wyeth Directors. Deferral Plan (including phantom shares attributable to dividend equivalents) will be converted into the right to receive an amount in cash equal to the per share value of the merger consideration, and all such non-employee director accounts will be paid out in cash, without interest and less any applicable taxes to be withheld, as soon as practicable after the effective time of the merger but in no event later than ten business days following the effective time of the merger, except in the case of certain accounts considered .grandfathered. under Section 409A of the Internal Revenue Code, which instead will be paid out in accordance with the applicable payment schedules provided under the terms of the Directors. Deferral Plan.

Also at the effective time of the merger, each phantom share of Wyeth common stock credited to any participant.s account under the Wyeth Supplemental Employee Savings Plan, the Wyeth 2005 (409A) Deferred Compensation Plan and the Wyeth Deferred Compensation Plan will be converted into phantom merger consideration, which, to the extent provided for under the terms of these plans, will become eligible to be reinvested in other phantom investment options provided for under these plans, to be paid (less tax withholding) to participants in such plans in accordance with the terms of the applicable plan and/or deferral and/or payment election form.

Also at the effective time of the merger, each outstanding right to receive a share of Wyeth common stock under the Wyeth Management Incentive Plan will be converted into a right to receive the merger consideration, payable in accordance with and subject to the terms of such plan.