The objective of this study is to obtain information on the effectiveness of thalidomide in psoriasis.

Inclusion Criteria:

• Male or female subjects 18 years of age or older.
• Stable or worsening psoriasis that involves 5% or greater of total body surface area (BSA) involvement with a minimum PASI score of 8.
• Moderate to severe plaque-type psoriasis, defined by a minimum score of 1 for each of erythema, scaling, and plaque thickness (using a 0 - 4 scale).
• Patients receiving systemic retinoids, prednisone, methotrexate, or cyclosporine should be on a stable dose at least 28 days prior to the first dose of thalidomide.
• Patients receiving topical treatments should be consistent with such treatments throughout the study.
• The ability and willingness to follow all study procedures, attend all scheduled visits, and successfully complete the study.
• The ability to understand and sign a written informed consent form, which must be obtained prior to treatment.
• The ability to understand, agree to, and comply with the requirements of the System for Thalidomide Education and Prescribing Safety (S.T.E.P.S.).**

(*Because of the known teratogenic effects of thalidomide and in an effort to prevent to the greatest extent possible any chance of fetal exposure to thalidomide, THALOMID(thalidomide) is approved for marketing only under a special restricted distribution program approved by the FDA. Under this program, the System for Thalidomide Education and Prescribing Safety (S.T.E.P.S.), only prescribers and pharmacists registered with the program are allowed to prescribe and dispense thalidomide (Zeldis JB et al. 1999). In addition, patients must be advised of, agree to, and comply with the requirements of the S.T.E.P.S. Program. To monitor patient compliance with the S.T.E.P.S. program, all patients must complete the S.T.E.P.S. program informed consent and participate in a mandatory and confidential surveillance registry.)

Exclusion Criteria:

• Unstable psoriasis
• Unable or unwilling to meet all criteria for contraception as required in STEPS.
• Known allergy to thalidomide.
• Known history of neuropathy.
• Abnormal laboratory test results that the investigator feels would compromise patient safety or evaluation of drug safety.
• The introduction of drugs for other medical conditions which are known to affect psoriasis (e.g., lithium, beta-adrenergic blockers, etc.) during the period 4 weeks prior to and during the study period.
• Use of any investigational therapy within the 4 weeks prior to the first dose of thalidomide.
• Expectation of exposure to strong sunlight during the course of the study (e.g. planned holiday in high sunlight area) or intention of sunbathing for prolonged periods of time during the course of the study.
• Current drug or alcohol abuse (drug screening not required).
• Medical conditions that preclude thalidomide therapy. Any other condition which, in the judgment of the investigator, would put the subject at unacceptable risk for participation in the study.