Sustained increases in glomerular capillary pressure and flow accompany systemic hypertension in rats that have undergone extensive ablation of the renal mass. These intrarenal hemodynamic changes are, in turn, associated with the progressive development of proteinuria and glomerular sclerosis, leading ultimately to failure of remnant nephron units. The efficacy of antihypertensive therapy with enalapril was evaluated in this animal model of chronic renal insufficiency. A dose of enalapril sufficient to prevent systemic hypertension normalized the glomerular capillary pressure without reducing the glomerular filtration rate in the remnant kidney. Maintenance of normal capillary pressure markedly reduced the development of proteinuria and sclerotic lesions in remnant glomeruli. These results suggest that antihypertensive therapy directed at reducing the glomerular capillary pressure could retard the progressive loss of renal function in patients whose functional renal mass has been reduced by disease.