In an attempt to characterize the clinical spectrum of renal insufficiency associated with nonsteroidal anti-inflammatory agents, 26 patients with 27 episodes of renal insufficiency secondary to these agents are described. These patients were seen over a 27-month period during which the inpatient distribution of these drugs by our hospital pharmacy was sufficient for approximately 92,000 patient-days of therapy. During these 27 episodes, serum creatinine increased from a mean value of 1.6 +/- .1 mg/dL to a mean maximum value of 3.3 +/- .3 mg/dL with a return to 1.7 +/- .1 mg/dL after discontinuation of the drug. Serum urea nitrogen increased from a mean of 27.8 +/- 2.5 mg/dL to 54.5 +/- 4.0 mg/dL and returned to 31.0 +/- 2.5 mg/dL. The mean duration of therapy in 25 patients was 4.2 +/- .7 days, and time to return to baseline renal function was 5.3 +/- .7 days. Five patients were briefly oliguric. No patient required dialysis. Only one patient had findings suggestive of interstitial nephritis. Patients were generally characterized by hemodynamic stress. In spite of only modest increases in serum creatinine, six patients had hyperkalemia with one sustaining a cardiac arrest secondary to a serum potassium of 7.9. We conclude that (1) the incidence of significant insufficiency in the general patient population is low but may be significant in a group characterized by hemodynamic stress; (2) the most common form of renal insult associated with nonsteroidal anti-inflammatory agents is mild renal insufficiency, which rapidly reverses when the agent is discontinued; and (3) hyperkalemia is relatively frequent, can be out of proportion to the degree of renal insufficiency, and can be life threatening.