A survey was carried out among an adult rural population of India to assess the prevalence of diabetes mellitus in undernourished population groups. The subjects subsisted on cereal-based diets inadequate in calories and most were underweight. The prevalence of diabetes, as assessed by the presence of glycosuria, was 2.4 per cent. No age differences were observed among men, whereas the prevalence was higher among women above fifty years of age. Of the women between twenty to fifty years of age, 49.3 per cent were lactating at the time of the survey. Out of these, 66.5 per cent had lactosuria, the maximum prevalence being observed in the first two years of lactation.