In this study, a 5 mg dose of CP-690,550 will be given to study subjects on two separate occasions using one of two different strength tablets each time. The amount of CP-690,550 available in the blood following administration of each tablet will be measured and compared. The overall aim of the study is to establish that a similar amount of CP-690,550 is absorbed into the blood following administration of the same dose of each different strength tablet .

This is a bioequivalence study for CP-690,550.

Inclusion Criteria:

• Healthy male and/or female (non-childbearing potential) subjects between the ages of 21 and 55 years, inclusive.
• Body Mass Index (BMI) of 17.5 to 30.5 kg/m2; and a total body weight >45 kg (99 lbs).
• No evidence of active or latent or inadequately treated infection with Mycobacterium tuberculosis (TB).

Exclusion Criteria:

Subjects with evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurologic, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at the time of dosing).

Personal or family history of hereditary immunodeficiency (eg, severe - Evidence of any clinically significant illness, medical condition, or disease.

• Evidence or history of any clinically significant infections within the past 3 months.
• Use of tobacco- or nicotine-containing products in excess of the equivalent of 5 cigarettes per day.