OBJECTIVE - To study the association between selected risk factors and the subsequent incidence of type II diabetes over a 5-yr period. RESEARCH DESIGN AND METHODS - Between 1973 and 1976, a cohort of men from 22 clinical centers throughout the U.S. enrolled in the Usual Care group of the Multiple Risk Factor Intervention Trial. The men (5420 white, 428 black, 56 Asian, 70 Hispanic, and 26 other) were nondiabetic at baseline, were in the upper 15% of risk for coronary heart disease, and had at least two annual follow-up visits for fasting glucose measurements. The average age was 46 yr and average body mass index was 27.6 kg/m2. Incidence of diabetes was defined as use of insulin or hypoglycemic agents, fasting glucose ≥140 mg/dl on two consecutive annual visits, or fasting glucose ≥140 mg/dl followed the next year by insulin or hypoglycemic use. Observations were taken annually over a 5-yr period. RESULTS - Cumulative incidence of diabetes over 5 yr was 4.1%, with 247 incident cases. Development of diabetes was directly associated with race (blacks higher than non-blacks), reported parental history of diabetes, and with baseline levels of body mass index, fasting glucose, and glucose 1 h after a 75-g oral glucose load. These associations were statistically significant in both univariate and multivariate models. A significant interaction was observed between race and reported parental history of diabetes in development of diabetes, particularly within black men who reported a parental history. These individuals had higher than expected rates of diabetes development. CONCLUSIONS - The data from men in the Usual Care group enrolled in the Multiple Risk Factor Intervention Trial confirm previous findings regarding the associations between the development of diabetes and baseline glucose levels, obesity, race, and parental history of diabetes. The identification of these risk factors provides very powerful tools to identify individuals at high risk of diabetes mellitus who may be amenable to intervention, thereby reducing their risk of developing the disease and its complications.