Evaluate the Efficacy and Safety of One Course of Amevive in Taiwan Patients

Inclusion Criteria: * Must give written informed consent * Must be \>= 16 years of age * Must have been diagnosed with chronic plaque psoriasis at least one year and require systemic or phototherapy * Must have CD4+ lymphocyte count at or above the lower limit of normal * Must have a BSA \>= 10% Exclusion Criteria: * Current erythrodermic, generalized pustular, or guttate psoriasis * Serious local infection or systemic infection within 3 months prior to the first dose of alefacept * History of any clinical significant disease that would be contraindicated for this study as determined by the investigator * Prior history of systemic malignancy, untreated localised skin canceer or a \>10 squamous cell carcinoma * Current enrollment in any other investigational drug study within 30 days prior to study drug administration * Treatment with systemic immunosuppressant agents within the 4 weeks prior to study drug administration.