In this study, the effects of inhibition of aldosterone on regression of existing hypertension-related glomerulosclerosis were investigated. Adult male Sprague Dawley rats (220 to 250 g) underwent 5/6 nephrectomy (Nx). Severity of glomerulosclerosis was assessed by renal biopsy 8 wk later, and rats were divided into four groups with equal biopsy sclerosis and then randomized by group to 4-wk treatments as follows: Control with no further treatment (CONT; n ‫؍‬ 6); spironolactone (SP) alone (200 mg/kg per d, by gavage, n ‫؍‬ 6); or SP combined with nonspecific triple antihypertensive drugs (TRX; reserpine, hydralazine, and hydrochlorothiazide in drinking water; SP؉TRX, n ‫؍‬ 7) or with angiotensin type 1 receptor antagonist (AT1RA; losartan in drinking water; SP؉AT1RA, n ‫؍‬ 8). When the rats were killed 12 wk after Nx, autopsy glomerulosclerosis index (SI; 0 to 4؉ scale) was compared with biopsy SI in the same rats. Systolic BP was increased at 8 wk after Nx and continued to increase at 12 wk after Nx in the CONT and SP groups but not in SP؉TRX-or SP؉AT1RA-treated rats. Serum creatinine at 12 wk was significantly decreased in all SP-treated groups versus CONT. CONT rats had on average a 157% increase in SI from biopsy to killing at 12 wk, compared with only 84% increase in SP rats, with regression of SI in some rats. The effects on glomerulosclerosis by SP were further enhanced (when systolic BP was controlled by TRX or by AT1RA). It is concluded that inhibition of aldosterone by SP not only slows development of glomerulosclerosis but also induces regression in some rats of existing glomerulosclerosis.