Assess the Long-term Effectiveness and Safety of Amevive (Alefacept) in Subjects With Moderate to Severe Chronic Plaque Psoriasis

Inclusion Criteria: * Subjects with moderate to severe chronic plaque psoriasis who receive a new prescription for alefacept Exclusion Criteria: * Subjects with a contraindication to alefacept * Subjects with a history of cancer except for adequately treated basal cell carcinoma (maximum of 2 lesions) * Subjects with any active cancer, including skin cancer * Subjects having a serious local infection (eg. cellulitis, abscess) or serious systemic infection (eg. pneumonia, septicemia, tuberculosis), within the 3 months prior to the first dose of alefacept. * Subjects known to be infected with the AIDS virus