In order to assess the quality of care in a community-wide sample of diabetic patients, a study was performed on 217 such patients identified in three group practices in an east London health district. Only 46% of the patients were currently attending a hospital. In the two years before review, 64% of patients had had their blood pressure recorded and 59% had had retinal examinations. Levels of glycosylated haemoglobin were significantly higher in patients on insulin than in those on oral regimes (P = 0.0004). The mean level of glycosylated haemoglobin was higher in patients from Social Classes III, IV, and V than in patients from Social Classes I and II (P = 0.005), but there was no difference in level between those patients attending hospital and those attending their general practitioners after accounting for differences in these two populations (P = 0.19). Over 50% of all diabetic patients in this study had levels of glycosylated haemoglobin which may indicate vulnerability to microvascular disease.