Cardiovascular disease risk factors were measured 10-15 years (mean, 11.9 years) prior to the diagnosis of impaired glucose tolerance and non-insulin-dependent diabetes mellitus in Rancho Bernardo, California. There were 1,847 men and women aged 40-79 years who had no known diabetes or fasting hyperglycemia at baseline (1972-1974). At the follow-up examination (1984-1987), 1,115 men and women (60.4%) had normal glucose tolerance, 513 (27.8%) had impaired glucose tolerance, and 219 (11.9%) had non-insulin-dependent diabetes mellitus as defined by World Health Organization criteria. Rates of impaired glucose tolerance and non-insulin-dependent diabetes mellitus increased with age, and impaired glucose tolerance was approximately twice as common as non-insulin-dependent diabetes mellitus. Those with non-insulin-dependent diabetes mellitus were older and more overweight and had higher levels of blood pressure, fasting plasma glucose, and triglyceride at baseline than those whose glucose tolerance remained normal; those with impaired glucose tolerance generally had intermediate levels of the same risk factors. When it was examined in a prospective fashion, in general, the age-adjusted risk of non-insulin-dependent diabetes mellitus increased with increasing quartile of each risk factor, and the risk of non-insulin-dependent diabetes mellitus in a given quartile was greater than that for impaired glucose tolerance. Logistic regression analyses showed these factors to be positively associated with a subsequent diagnosis of impaired glucose tolerance as well as non-insulin-dependent diabetes mellitus in women, and to a lesser degree in men, independent of baseline age and body mass index (weight (kg)/height (m)2). These data illustrate that a less favorable cardiovascular risk factor profile precedes the diagnosis of both non-insulin-dependent diabetes mellitus and impaired glucose tolerance.