Microalbuminuria indicates slightly elevated urinary albumin excretion. In most cases, microalbuminuria is of glomerular origin and indicates initial glomerulosclerosis. Microalbuminuria has a high predictive value for nephropathy in insulin-dependent diabetes subjects and for premature mortality due to cardiovascular disease in non-insulin-dependent diabetes subjects and in the general population. All cardiovascular risk factors can be determinants for microalbuminuria constitution, especially the genetic determinants of these risk factors. Thus, microalbuminuria can be an indicator to summarize renal or cardiovascular risk, or both, in various populations. Treatment interventions were performed using microalbuminuria as the endpoint. So far, the most convincing results were obtained with angiotensin I-converting enzyme inhibitors to prevent nephropathy in insulin-dependent diabetes subjects.