The safety and efficacy of 3% topical minoxidil were evaluated in the treatment of extensive patchy alopecia areata, alopecia totalis, and alopecia universalis. Patients with extensive patchy alopecia areata had greater than 50% scalp hair loss. In this double-blind study, thirty subjects applied minoxidil or placebo to half of the afflicted scalp area twice daily, with overnight petrolatum occlusion, for 1 year. Both male and female subjects, ranging in age from 9 to 65 years, were enrolled, fifteen subjects to each treatment group. Minoxidil applications were generally well tolerated except for three instances of scalp itching and dermatitis, two of which necessitated discontinuing the medication. Hair growth was seen in seven of eleven evaluable subjects (63.6%) in the minoxidil group and in five of fourteen evaluable subjects (35.7%) in the placebo group. Excellent, cosmetically acceptable hair growth was seen in three of eleven minoxidil-treated subjects (27.3%) and in one of fourteen placebo-treated subjects (7.1%). Examination of vital signs and laboratory measurements revealed no evidence of systemic effects of minoxidil. Seven of the twelve subjects assayed in the minoxidil group had detectable minoxidil serum levels, ranging from 0.4 to 7.5 ng/ml.