The prevalence of diabetes in subjects aged 18 yr and over was evaluated in a rural community of Southern Italy (Sanza). Among the 1,154 participants examined by using a 75 g oral glucose load according to the recent WHO diagnostic criteria, the diabetes prevalence was 6.6% in men and 6.8% in women; impaired glucose tolerance occurred in 5.1% of men and 7.9% of women. The frequency of positive family history of diabetes was no higher in subjects with diabetes and impaired glucose tolerance, than in controls. Obesity was clearly related to diabetes (p less than 0.05 in men and p less than 0.01 in women 40 yr old and over). The level of physical activity was significantly lower in subjects with diabetes than in normal subjects. The results suggest that a remarkable reduction in physical activity, along with an increased caloric intake, may have importance in determining the prevalence and time of appearance of non-insulin-dependent diabetes.