1259 Tanzanians in a provincial town were examined for varicose veins. 5-5% (6-1% of men and 5-0% of women) of the 1000 people aged eighteen years and over had varicose veins. This prevalence is intermediate between that reported for minimally developed areas (0-1%-0-4%) and the age-adjusted rate reported for Michigan (12-3%). The Tanzanian diet included some refined carbohydrate, and the mean daily stool weight (228 g) indicated a fibre content intermediate between that of traditional African communities (490 g) and western countries (115 g). These findings are consistent with the hypothesis relating varicosities to a fibre-depleted diet. Life-long use of the squatting position for defaecation did not protect against the development of varicose veins.