The clinical features of 47 frail nursing home diabetic patients with a mean age of 81 +/- 1.6 years were compared to those of 61 nondiabetic nursing home residents with a mean age of 80.2 +/- 1.2 years. Diabetic patients had a higher prevalence of renal failure, proteinuria, retinopathy, neuropathy, and infections than did other nursing home residents. Macroangiopathic disease tended to be equally common in both age groups. Diabetic nursing home residents had higher body weights compared to nondiabetic nursing home residents. Surprisingly, however, 21% of nursing home diabetics were greater than 20% below average body weight (compared to 24.5% of other nursing home residents), suggesting that undernutrition is a major problem in diabetic patients in a nursing home setting. Overall, the diabetic nursing home patients had better blood glucose control than younger ambulatory diabetic patients (mean age 66.2 +/- 4.7 years). The glycosylated hemoglobin (HbA1) level in those on oral agents was 8.9% +/- 0.7% for nursing home patients compared to 11.8% +/- 0.7% in ambulatory patients (P less than 0.01). The HbA1 in insulin-treated patients was similarly lower in nursing home diabetics (9.6% +/- 0.4% vs 11.8% +/- 0.7, P less than 0.05). There were only two mild hypoglycemic episodes in nursing home patients over 6-month observation period, whereas 12 ambulatory patients reported hypoglycemic episodes during the same period of time. We conclude that although the diabetic nursing home patients are sicker than the ambulatory diabetics, it is possible to achieve a fair blood glucose control in nursing home patients without a significant risk of recurrent hypoglycemia.