Renal effects of enalapril maleate in ten hypertensive patients with glomerulonephritis were evaluated after 1 and 16 weeks of therapy. Systemic blood pressure decreased, glomerular filtration rate was not significantly changed, and sodium fractional excretion and renal plasma flow increased, whereas renal vascular resistances and filtration fraction decreased acutely at the end of the study. Proteinuria diminished, but no variations in qualitative pattern were observed. ACE inhibitors, promoting efferent rather than afferent arteriolar vasodilatation and reduction of glomerular permeability coefficient, may reduce glomerular capillary hypertension and the development of proteinuria.