A randomized double-blind trial of topical minoxidil was carried out during a 12-month period in 56 patients with male pattern baldness. Subjects were randomly assigned to treatment with either 2% minoxidil solution, 3% minoxidil solution, or placebo. The placebo group was switched to 3% minoxidil after the first 4 months. Subjects using the 2% and 3% solutions of minoxidil showed a significant change in terminal and indeterminate hair counts (p less than 0.05) from the placebo group at 4 months. A progressive decrease in vellus hair counts with a concomitant increase in both indeterminate and terminal hair counts was noted during the 12-month period, suggesting that minoxidil applied topically partially reverses the balding phenomenon.