Forty-one men with male pattern baldness completed 132 study weeks (2 years 9 months) with topical minoxidil and had follow-up 1-inch target-area vertex scalp hair counts. Initially these men were treated with either twice-daily 2% topical minoxidil for 12 months or 3% topical minoxidil for 8 to 12 months (one third of the subjects received placebo for the first 4 months). After 12 months all subjects continued to apply 3% topical minoxidil twice daily for 1 more year, after which they were randomized to once- versus twice-daily topical minoxidil for an additional 9 months. Those subjects who changed to once-daily application of topical minoxidil at 2 years had a mean change from baseline nonvellus hair count at 1 year of 291.2 (range of hairs four to 553) and at 2 years 9 months of 235 (two to 592 hairs). Those subjects who continued with twice-daily application of topical minoxidil throughout the study had a mean change from baseline nonvellus hair count at 1 year of 323 (15 to 589 hairs) and 335 (13 to 808 hairs) at 2 years 9 months with maintenance topical minoxidil. There were subjects on both maintenance schedules of topical minoxidil who lost some of the nonvellus hair they had initially gained with topical minoxidil; however, there was a greater mean loss in those patients following the once-daily versus twice-daily topical minoxidil regimen (p = 0.05). No subject lost nonvellus target hair as compared with baseline.(ABSTRACT TRUNCATED AT 250 WORDS)