Microalbuminuria (MA) is defined as a persistent elevation of albumin in the urine of >30 to <300 mg/d (>20 to <200 microg/min). Use of the morning spot urine test for albumin-to-creatinine measurement (mg/g) is recommended as the preferred screening strategy for all patients with diabetes and with the metabolic syndrome and hypertension. MA should be assessed annually in all patients and every 6 months within the first year of treatment to monitor the impact of antihypertensive therapy. It is an established risk marker for the presence of cardiovascular disease and predicts progression of nephropathy when it increases to frank microalbuminuria>300 mg/d. Data support the concept that the presence of MA is the kidney's warning that there is a problem with the vasculature. The presence of MA is a marker of endothelial dysfunction and a predictor of increased cardiovascular risk. MA can be reduced, and progression to overt proteinuria prevented, by aggressive blood pressure reduction, especially with a regimen based on medications that block the renin-angiotensin-aldosterone system, and control of diabetes. The National Kidney Foundation recommends that blood pressure levels be maintained at or below 130/80 mm Hg in anyone with diabetes or kidney disease.