The prevalence of non-insulin-dependent diabetes mellitus in 1467 ambulatory elderly subjects aged from 60 to 90 years was determined using fasting plasma glucose as a screening test. A questionnaire survey on the history of diabetes and related complications was performed. The results showed that 10.7% had already been diagnosed as having diabetes mellitus. Screening revealed a further 5% who had diabetes mellitus but were asymptomatic. The prevalence of non-insulin-dependent diabetes mellitus was 15% (95% confidence interval 9-21) among the 60- to 80-year-old age group and 17% confidence interval (3 to 30) in those older than 80 years. Obesity and advancing age were adverse risk factors associated with diabetes. The diabetic subjects had significantly more coronary and cerebrovascular atherosclerosis, hypertension, and adverse lipid profiles. Even in the non-diabetic elderly subjects, fasting blood glucose was positively correlated with body weight and body mass index, confirming the importance in the aetiology of non-insulin-dependent diabetes mellitus. This is a common disease in the elderly and is associated with significant cardiovascular morbidity.