Chronic renal failure was modeled in rats by partial nephrectomy. Blood pressure, heart rate, concentrations of aldosterone, urea, creatinine, electrolytes, and protein, index of hypertrophy of visceral organs, and 24-h diuresis were evaluated. In rats treated with spironolactone, the index of myocardial hypertrophy did not considerably differ from that in sham-operated animals, whereas in untreated rats the test parameters considerably differ from the control. We concluded that the blockade of aldosterone receptors with spironolactone produced a cardioprotective effect in Wistar rats with subtotal nephrectomy.