Risk factors measured in a cross-sectional study in subjects aged 65-74 years living in eastern Finland were correlated with the risk of developing diabetes 3.5 years later. Sixty-nine of 892 initially non-diabetic subjects developed diabetes during the follow-up. Subjects who subsequently developed diabetes had multiple adverse changes in risk factor levels before the diagnosis of diabetes. Subjects who developed diabetes had higher body mass index and waist-hip ratio as well as higher levels of fasting and 2-h plasma glucose and insulin and higher prevalence of family history of diabetes than those who remained healthy. Furthermore, prevalence of hypertension and levels of diastolic blood pressure and total triglycerides were higher and HDL cholesterol lower among subjects who developed diabetes than among those who remained healthy. The highest risk of developing diabetes was associated with impaired glucose tolerance (World Health Organisation criteria) (odds ratio = 9.8, 95% confidence interval = 6.1-5.8). The risk of developing diabetes was 3.7 (3.2-6.1) among subjects in the highest quartile of 2-h insulin distribution, 3.5 (2.0-6.1) in those with triglycerides greater than 2.5 mmol/l, 2.7 (1.5-4.6) in those with waist-hip ratio greater than 1.0, 2.5 (1.5-4.4) in those with HDL cholesterol less than 1.0 mmol/l, 2.1 (1.2-3.6) in those with body mass index greater than 30 kg/m2, 1.9 (1.1-3.3) among those in the highest quartile of fasting insulin distribution, 1.8 (1.0-3.1) in those having hypertension, and 1.7 (1.0-2.9) in those with a family history of diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)