1. To study the difference in sweat rate between men and women the rates of cholinergic-induced sweating were measured in normal people before and after puberty and in response to androgens and anti-androgens. 2. Sweat rate in men was more than double that in women. 3. This difference did not occur in prepubertal boys and girls in whom the rate, corrected for surface area, was comparable with that in women. 4. Application or injection of androgen locally did not stimulate sweat production in the adult female. 5. Anti-androgen topically or systemically did not decrease sweat rate in men. 6. It is concluded that the rate of sweat rate in men is caused by androgen-induced gene expression at puberty and not by androgen modulation in adult life.