A Study To Evaluate The Effects And Safety Of Treatment, Treatment Withdrawal, Followed By Re-Treatment With CP-690,550 In Subjects With Moderate To Severe Chronic Plaque Psoriasis

Inclusion Criteria:

- 18 years or older with diagnosis of plaque-type psoriasis (psoriasis vulgaris) for at
least 12 months prior to first dose of study drug;

- Psoriasis Area and Severity Index (PASI) score of 12 or greater, AND Physician's
Global Assessment (PGA) score of 3 (moderate) or 4 (severe); Psoriasis covering at
least 10% of body surface area;

- No evidence of active or latent or inadequately treated infection with Tuberculosis or
other serious infections.

Exclusion Criteria:

- Non-plaque or drug induced forms of psoriasis;

- Cannot discontinue current oral, injectable or topical therapy for psoriasis or cannot
discontinue phototherapy (Psoralen Ultraviolet A; Ultraviolet B).

- Any uncontrolled significant medical condition.