Abstract
A patient who was subsequently shown to have stenosis of the artery to a transplanted kidney sustained three episodes of impaired renal function during treatment with low doses of captopril. On each occasion this was reversed by withdrawal of therapy. The effect was not related to reduction of blood pressure since lower pressures were recorded during treatment with minoxidil, without deterioration of renal function. A possible mechanism involving blockade of the intrarenal renin-angiotensin system is discussed.