Minoxidil, a potent peripheral vasodilator used orally for refractory hypertension, has produced hypertrichosis. To determine the efficacy and safety of 1% or 5% topical minoxidil for the stimulation of scalp hair regrowth, we studied fifteen normotensive patients, five with androgenic alopecia and ten with alopecia areata diagnosed clinically and by biopsy, for 12 months. Three of five patients with androgenic alopecia using 5% minoxidil for 12 months noted hair regrowth, ranging from minimally observable hair to an appreciable restoration of larger, pigmented, terminal hair in one patient. Among the patients with androgenic alopecia, regrowth response corresponded to the serum minoxidil blood levels. None of the patients with alopecia areata receiving either 1% or 5% minoxidil noted hair regrowth despite comparable minoxidil blood levels. Improved local absorption of topical minoxidil solution may promote hair regrowth in androgenic alopecia.