A double-blind, parallel comparison was made of the short-term efficacy and safety of three times daily regimens of 0.05% clobetasol propionate cream and 0.05% fluocinonide cream in 114 adolescent and adult patients with psoriasis and 113 with eczema. After 2 weeks of topical applications, patients were assessed according to (1) investigators' overall judgment of clinical response, (2) degree of severity of specific signs and symptoms, and (3) patients' evaluation of improvement. In all three response categories in psoriasis, and in two of three in eczema, clobetasol was statistically significantly superior to fluocinonide (p less than 0.05-p less than 0.001). Healing commenced more rapidly with clobetasol and there was no indication of tachyphylaxis. In contrast, the healing rate with fluocinonide slowed noticeably after the first week, and there was a greater tendency to relapse following fluocinonide treatment. Both regimens were safe: drug-related side effects were generally mild and occurred most commonly with fluocinonide therapy in eczema patients. Overall, drug-related effects occurred in 4% of patients receiving clobetasol and 12% receiving fluocinonide (p less than 0.05). Transient morning plasma cortisol reductions below 5 micrograms/dl occurred in 6% of clobetasol-treated patients, reverting to normal within 1 week of the end of treatment.