AbstractProcyanidin B‐2 is a compound we have identified in apple which acts as a growth‐promoting factor on murine hair epithelial cells. This report describes our investigation of the hair‐growing effects of 1% procyanidin B‐2 tonic after sequential use for 4 months. A double‐blind clinical trial was performed, involving a total of 29 subjects (procyanidin B‐2, 19 men; placebo, 10 men). No adverse side effects were observed in either group. In the procyanidin B‐2 group, 78.9% showed an increased mean value of hair diameter, whereas only 30.0% in the placebo group showed any increase (p < 0.02, Fisher's exact probability test). The increased ratio of hairs measuring more than 40 μm in diameter after 4 months of procyanidin B‐2 treatment was significantly higher than that of the placebo controls (p < 0.05, two‐sample­t‐test). The increase in number of total hairs in the designated scalp area (0.25 cm2) of procyanidin B‐2 subjects after a 4 month trial was significantly greater than that of the placebo controls (procyanidin­B‐2, 3.67 ± 4.09 (mean ± SD)/0.25 cm2; placebo, −2.54 ± 4.00/0.25 cm2; p < 0.001, two‐sample t‐test). Procyanidin B‐2 therapy shows potential as a promising cure for male pattern baldness. Copyright © 2001 John Wiley & Sons, Ltd.