Diuretics have been used in acute renal failure in an attempt to increase urine flow and ameliorate the reduction in glomerular filtrate rate. A beneficial response occurs in some experimental models of acute renal failure when diuretics are administered prophylactically or very early in the course of renal failure and may require a renal vascular bed capable of responding partially, at least, to vasodilating stimuli. In chronic renal insufficiency the most important indications for diuretic use are for the treatment of systemic hypertension and for the correction of the congested state. However, the precise effect of diuretic therapy under these conditions is unpredictable and dependent on the functional state of the renal vessels. Diuretic administration may at times prove detrimental, resulting in a deterioration of glomerular filtration rate. In hemodynamically unstable conditions the slow removal of extracellular fluid by continuous arteriovenous hemofiltration may prove preferable to diuretic administration or standard forms of dialysis.