SummaryDiabetic nephropathy is the most important cause of increased morbidity and premature mortality in patients with insulin dependent diabetes mcllitus. Several longitudinal studies done in different countries have shown that microalbuminuria strongly predicts the development of diabetic nephropathy in insulin dependent diabetes mellitus.Very few data arc available about the situation in Belgium. In a retrospective study we analysed the data of 271 insulin dependent diabetic patients attending the University Hospital of Antwerp during the year 1994. Normoaibuminuria was defined as a urinary albumin excretion rate of200 ng/min.In our population we find an overall prevalence of microalbuminuria of 14%. Patients with microalbuminuria are characterised by an earlier onset and i longer duration of diabetes when compared with patients with normoaibuminuria. Further we find that they have a worse glycemic control, a higher frequency of raised arterial blood pressure and a higher percentage of proliferative retinopathy. These data are comparable with those from other studies done in different countries. They show that patients with microalbuminuria should be regarded as a high risk group and therefore urinary albumin excretion rate should be monitored routinely. Also they stress the importance to strive to a good metabolic control and to an aggressive treatment of arterial hypertension.