Ischemic renal disease (IRD) is defined as a clinically important reduction in glomerular filtration rate or loss of renal parenchyma caused by hemodynamically significant renal artery stenosis. IRD is a common and often overlooked clinical entity that presents itself in the setting of extrarenal arteriosclerotic vascular disease in older individuals with azotemia. Eleven to 14% of end-stage renal disease (ESRD) cases are attributable to chronic IRD. A high percentage of patients entering ESRD programs are hypertensive. Many patients with a presumed diagnosis of hypertensive nephrosclerosis actually have undiagnosed ischemic nephropathy as the etiology of their ESRD. It is important for the clinician to identify IRD, because IRD is a potentially reversible cause of chronic renal failure in a hypertensive patient. Atherosclerotic renal artery disease is common among patients with coronary artery disease and aortic and peripheral vascular disease. Atherosclerotic renal artery disease is a progressive disorder, and its progression is associated with loss of renal mass and functioning. A decrease in glomerular filtration rate sufficient to cause an elevation of the serum creatinine concentration requires injury to both kidneys. Consequently, IRD can arise from one of two main clinical situations: bilateral hemodynamically significant renal artery stenosis leading to bilateral renal ischemia; and hemodynamically significant renal artery stenosis in a solitary functioning kidney, or in a kidney that is providing the majority of a patient's glomerular filtration. The primary reason for establishing the diagnosis of IRD is the hope that correction of a renal artery stenosis will lead to improvement of renal function, or a delay in progression to ESRD. There are six major clinical settings in which the clinician could suspect IRD: acute renal failure caused by the treatment of hypertension, especially with angiotensin converting enzyme inhibitors; progressive azotemia in a patient with known renovascular hypertension; acute pulmonary edema superimposed upon poorly controlled hypertension and renal failure; progressive azotemia in an elderly patient with refractory or severe hypertension; progressive azotemia in an elderly patient with evidence of atherosclerotic disease; and unexplained progressive azotemia in an elderly patient. Noninvasive testing modalities that have been used recently include the angiotensin converting enzyme inhibitor renal scan, duplex Doppler sonography, magnetic resonance angiography, and the spiral computed tomography. Treatment methods include percutaneous transluminal angioplasty, endovascular stenting, and surgical revascularization. The results of treatment for preservation of renal function have been encouraging, with stabilization or improvement in renal function observed in a significant proportion of cases.