Urinothorax is a rare complication of blunt renal trauma, ureteral instrumentation or ureteral surgery. A leakage from the urinary tract causes urinoma, a retroperitoneal collection of fluid, which can lead to urinothorax. We report a patient with solitary kidney who underwent extracorporeal shock wave lithotripsy (ESWL) for nephrolithiasis. Four days after ESWL, she had right-sided pleural effusion which demonstrated as urinothorax. Urinoma occurring after ESWL, as in our case, is a situation that has not been reported before as a cause of urinothorax. Urinothorax should be taken into consideration in patients with pleural effusion who recently underwent ESWL. Copyright (C) 2002 S. Karger AG, Basel.