Fourteen patients were studied 2 to 36 months after acute tubular necrosis. It was observed that 43% of the patients had decreased glomerular filtration rate. These patients were older and had lower urinary excretion of ammonium and titratable acidity. Proteinuria greater than 150 mg/day, without reaching a nephrotic level, was found in 92% of the patients. The presence of oliguria, the demand of dialysis, and the acute tubular necrosis etiology were not statistically different among the patients who recovered their glomerular filtration rate either totally or partially.