Sweat secretion rate (SSR) was measured by the pilocarpine iontophoresis test in (a) 254 healthy children and adolescents (aged 6.0 to 19.2 years, mean age 11.2 years); in (b) 58 healthy adults (aged 20.4 to 75.2 years, mean age 37.6 years); and in (c) eight prepubertal patients with growth hormone (GH) deficiency (aged 4.2 to 13.5 years, mean age 8.9 years). Boys had higher median values for SSR than girls (pre-pubertal children: 92.7 vs 64.5 mg 30 min-1 pubertal children: 110.3 vs 73.1 mg 30 min-1), and men showed higher values than women (135.5 vs 49.2 mg 30 min-1). In addition, the change in sweat excretion rate from childhood to adulthood showed a difference between the sexes. Both pre-pubertal and pubertal boys had a lower secretion value than adult men (p less than 0.001 and 0.01, respectively), whereas girls showed higher secretion values than adult women (p less than 0.01 and p less than 0.001, respectively). There was a significant increase in SSR from prepuberty to puberty (p less than 0.001) for both sexes. The children with GH deficiency, all pre-pubertal, showed significantly reduced SSR (p less than 0.001) compared with the healthy children (median values: 32.8 vs 80.0 mg 30 min-1). We conclude that (a) sweat secretion pattern in children shows a significant sex difference and (b) sweating in children is dependent on growth hormone.