Microalbuminuria (Mi) is thought to reflect diffuse vascular damage and to predict cardiovascular morbidity and mortality in essential hypertension, although its pathogenesis remains to be fully elucidated. The relationship between microalbuminuria and several cardiovascular risk factors and target organ damage was evaluated in a large cohort of untreated essential hypertensive patients. Albuminuria was measured as the albumin to creatinine ratio in three non consecutive first morning urine samples. Cardiac damage was evaluated by ECG and retinal vascular changes by direct ophtalmoscopy. In a subgroup of 23 patients with Mi and in a control group of 22 normoalbuminurics, selected from the entire cohort of patients and carefully matched for age, gender, body mass index (BMI) and duration of disease, we also measured left ventricular mass index by M-B mode echocardiography, common carotid wall thickness by high resolution US-scan, and renal vascular resistances by US-doppler of interlobar arteries. K-means cluster analysis performed on the entire cohort of patients showed that microalbuminuria is associated with the presence of an unfavorable risk profile and target organ damage. Furthermore, microalbuminuric hypertensive patients have a larger left ventricular mass index, increased intima media thickness of carotid arteries and higher intrarenal vascular resistances as compared to a well matched group of normoalbuminuric patients. We conclude that in essential hypertension increased urinary albumin excretion can be useful to identify patients for whom more aggressive preventive strategies and/or additional treatment measures are advisable.