Factors predicting impared glucose tolerance (IGT) and diabetes (DM) were studied in a community-living population aged 70 years or over, with initial normal glucose tolerance (NGT). The baseline examinations from 1991 to 1992 included an oral glucose tolerance test (OGTT), physical examinations and questionnaires. The follow-up examinations in 1994 and 1995 comprised of an OGTT. One hundred and thirteen of the eligible 134 subjects, with baseline NGT, participated in the re-examinations. Thirty six percent of these subjects progressed to IGT and 3% to DM. Obesity was the best predictor of IGT or DM, and central obesity was also associated with them. In addition, abnormal progression of glucose tolerance was also associated with those aged greater than 80 years, with systolic blood pressure greater than 160 mmHg, diastolic blood pressure greater than 80 mmHg, fasting blood glucose value of greater than 5.3 mmol/l, and 2 h of blood glucose value greater than 6.8 mmol/l.