Gonadal and gonadotrophic hormones were assayed in members of !Kung population who live in north-western Ngamiland, Botswana, and who are true San ('Bushmen') hunter-gatherers. An attempt was made to correlate their hormonal secretion and morphology. Peripheral serum levels of gonadotrophins and gonadal steroids were measured by means of radio-immune methods. Female San appear to have suppressed circulating levels of gonadal steroids, while gonadotrophins were in the normal range. No evidence for elevated circulating levels of oestrogen could be found. Male San showed hormone levels similar to Caucasoid and Negro ('Bantu') values.