The present study was designed to evaluate the urinary albumin excretion in 62 patients with essential hypertension. None of them had prior proteinuria or history of nephropathy or uropathy. Patient data, blood pressure, proteinuria using Bradford's method, albuminuria by radial immunodiffusion, urinary SDS-PAA electrophoresis, plasma glucose, serum creatinine, serum cholesterol were determined. The urinary albumin excretion was significantly higher (p < 0.001) in the group of hypertensive patients (19.22 +/- 2.36 micrograms/min) compared to a group of 20 control subjects (4.17 +/- 0.67 microgram/min). Compared to a subgroup of hypertensive patients without ischemic heart disease (12.07 +/- 1.30 micrograms/min) microalbuminuria was higher (43.74 +/- +/- 5.74 micrograms/min; p < 0.001) in a subgroup of 14 patients with essential hypertension and ischemic heart disease with severe coronary events: unstable angina pectoris (9 patients), myocardial reinfarction (2 patients), ventricular arrhythmias (3 patients). A positive correlation between the microalbuminuria and the duration of hypertension was found (r = 0.64; p < 0.001). Therefore, microalbuminuria may represent a marker of the severity of vascular involvement in hypertensive patients.