In a controlled, randomized double-blind study, 51 patients with androgenetic alopecia and increased hair loss (telogen rate > 20%) were treated by local application of hair lotions with and without 17α-estradiol (0.025%) for a period of at least 6 months. Before and after therapy trichograms were taken and evaluated under standardized conditions. In 63% of the treated patients a reduction of the amount of telogen hairs appeared, whereas in the control group the same reduction was found in only 37% of the cases. Similarly, in the treated group only 11% of the patients worsened, in contrast to 50% of the control group who showed an increased telogen rate (> 10%). The amount of growing anagen hairs and of seborrhea did not change significantly in both groups. Side effects were not seen. These findings indicate that hair lotions containing 17α-estradiol may have a therapeutic value in reducing androgenetic hair loss, if applied topically for a long period of time, similar to 17β-estradiol. However, no regrowth of new hair was fou