Chronic renal insufficiency ultimately culminating in end-stage renal disease requiring dialysis or transplantation is a major health problem in the United States. The first task confronting the physician caring for a patient with renal disease is to decide whether the renal insufficiency is acute or chronic. The initial differential diagnostic approach to chronic renal insufficiency consists of determining whether the patient has glomerular disease or interstitial or vascular disease on the basis of a careful history taking, urinalysis, and measurement of 24-hour protein excretion. Further refinement of diagnostic considerations often requires serologic studies, renal biopsy, or imaging the urinary tract with ultrasonography or computed tomography. Management considerations begin with the identification and correction of any acute reversible causes of renal insufficiency in patients with chronic renal disease. Recent studies have shown that effective antihypertensive therapy, especially with angiotensin-converting enzyme inhibitors, restriction of dietary protein, and excellent glycemic control in patients with diabetes, can retard the progression of chronic renal disease. Once these therapeutic strategies are in place, it is important to anticipate and treat the multiple manifestations of chronic progressive renal insufficiency: fluid overload, hyperkalemia, metabolic acidosis, abnormalities of calcium, phosphorus, and vitamin D metabolism, and anemia.