The purpose of this study is to assess the safety, pharmacokinetics and clinical activity and immunogenicity of BMS-188667 (CTLA4Ig) in subjects with psoriasis vulgaris

Inclusion Criteria:

• Diagnosis and documentation of a history of stable psoriasis vulgaris of at least 6 months duration.
• vulgaris total body surfae area involvement of at least 10%
• Failure for toxicity and/or inefficacy of at least one standard anti- psoriatic therapy including topical treatment, phototherapy, photochemotherapy, methotrexate, cyclosporin A or etretinate.

Exclusion Criteria:

• Male and female subjects who are not willing to receive adequate counseling and exercise adequate contraceptive measures with enrolle on study.
• Functional class (V (ACR) RA or amyloidosis)
• Active vasculitis (except for subcutaneous rheumatoid nodules).
• Subjects with a history of asthma, angioedema or anaphylaxis.
• Subjects with evidence of active or latent bacterial or viral invedtions.
• Subjects with a history or malignancy (except basal cell or superficial squamous cell skin carcinoma).
• body weight > 100 kg (or 220 lbs.)