Seventy-seven patients with psoriasis vulgaris were treated with methotrexate administered orally, and their conditions evaluated for evidence of hematopoietic and hepatic toxicity. Sixteen psoriatic patients not treated with methotrexate and 14 patients without psoriasis or significant systemic illness were used as controls. No significant bone marrow depression was observed. Of the patients treated, 43% (33) had elevated lactic acid dehydrogenase levels, 25% (19) had elevated serum glutamic oxaloacetic transaminase levels, and 5% (4) had elevated alkaline phosphatase levels. All abnormal chemistries returned to normal within one month of cessation of methotrexate therapy. Clinical results with methotrexate therapy were gratifying at the dosage levels used, in that 84% (64) of the patients had a satisfactory response.