The screening for microalbuminuria in diabetic patients has been made possible by means of sufficiently sensitive and reproducible techniques. Threshold values of albumin excretion rate must be defined according to the type of urine collection and by taking into account the high variability of this parameter. The high variability of albumin excretion rate required that repeated measurements must be considered. The prevalence of microalbuminuria depends on the type of diabetes, the degree of micro- and macrovascular complications, and the presence of associated arterial hypertension. Current attempts to reduce microalbuminuria in the diabetic patients through strict glycaemic control, lowering of high blood pressure and other means, are discussed.