Oral glucose tolerance was studied following a 75 g glucose load in 108 (82.4%) of 131 male and 110 (79.1%) of 139 female members of a Hindu subcommunity aged 15 years and over in Dar es Salaam. One year later, the glucose tolerance tests were repeated in 93 (86.1%) and 93 (84.5%) of the 108 male, and 110 of the female subjects, respectively. In the first survey, 25 (26.9%) of the 93 male and 24 (25.8%) of the 93 female subjects had impaired glucose tolerance (IGT), 6 (6.4%) and 15 (16.1%), respectively, had diabetes mellitus; and 62 (66.7%) and 54 (58.1%), respectively, had normal glucose tolerance. In the repeat survey, of the 93 male and 93 female subjects, 8 (8.6%) and 7 (7.5%) had IGT, 4 (4.3%) and 10 (10.8%) had diabetes; and 81 (87.1%) and 76 (81.7%) were normal, respectively. Of the 21 subjects diagnosed as having diabetes in the first survey, 13 (61.9%) continued to show diabetic glucose tolerance; 4 (19%) IGT and 4 (19%) had normal glucose tolerance with no gender difference. One (1.6%) of the 62 male subjects and none of the 54 females with normal glucose tolerance in the first survey progressed to IGT, while the remainder retained normal glucose tolerance. Diabetes and IGT rates in both surveys were higher for the older than the younger persons. A significant fall in mean fasting and post-75 g blood glucose levels, and in mean systolic and diastolic pressure levels was observed between the first and second surveys in both genders. There was, however, no significant difference in body mass index (BMI), serum total cholesterol and triglyceride levels between surveys, suggesting that major dietary changes had not taken place. Male subjects who showed persistent IGT had significantly lower mean level of body mass index (kg/m2) than subjects who reverted to normal, whilst for the whole group those who had persistent IGT were older. It is tempting to speculate that these changes were due to community action. However, in view of the lack of change in weight and lipids and similar results in other communities in Tanzania when retested at 1 week, further studies are needed to establish the significance of the findings.