In this report, we present the case history of a patient who developed a brief period of oliguria following acute tubular necrosis. Obstructive uropathy and renal underperfusion were ruled out as etiologic causes of oliguria. While glomerular filtration rate (GFR) returned rapidly toward normal, an unusually prolonged and massive diuresis and saluresis (as high as 45 liters/24 h and 5,700 mEq Na/24 h) ensured for almost 1 month; following this, remission was completed over a matter of days. We believe this case dramatically illustrates the importance of functional maturation of tubules in recovery from acute tubular necrosis, and the protective effect against excess fluid and salt losses afforded by decrease in GFR usually seen in this syndrome.