Seven patients with glomerular proteinuria and hypertension (six with biopsy confirmation of glomerulonephritis, one with proteinuria after unilateral nephrectomy) were randomly given, for 14 days each, a calcium antagonist and then a conversion enzyme inhibitor, or vice versa, following a 14-day pause of all medication. Fractional albuminuria rose significantly during administration of calcium antagonists (P less than 0.05), while it decreased significantly during administration of converting enzyme inhibitor (P less than 0.05). The explanation for this finding may be that calcium antagonists raise glomerular capillary pressure by dilating the afferent arterioles, while converting enzyme inhibitors predominantly cause dilatation of the efferent arterioles.