Course, prognosis and mortality in Japanese elderly diabetes mellitus were studied using a 7 year follow-up study of 424 elderly diabetics whose ages were 60 years old or more (mean age: 72.6 +/- 6.2, 144 males: 280 females) at baseline. The relationships between clinical findings at baseline and prognosis, causes of death and onset of ischemic heart disease during the follow-up period were also studied. A total of 133 (31%) deaths were observed during the follow-up period. Risk factors present at baseline which significantly influenced the patients' prognosis included age, male gender, previous cerebro-vascular disease, body mass index, pharmacological treatment of diabetes and persistent proteinuria. These factors were also related to the causes of death among the patients. Cardio-vascular disease deaths (n = 66, 50%) tended to increase in patients with a relatively higher age, male gender, previous ischemic heart disease and persistent proteinuria. Malignant neoplasm deaths (n = 28, 21%) tended to increase in patients with relatively higher age and previous cerebrovascular disease. Furthermore, infectious deaths (n = 16, 12%) were relatively increased in patients with a relatively higher age, male gender, previous cerebro-vascular disease, relatively lower body mass index and higher fasting plasma glucose levels. Among various causes for cardio-vascular disease deaths, ischemic heart disease (n = 40) was the leading cause of death.(ABSTRACT TRUNCATED AT 250 WORDS)