A case of urinothorax is reported in a 19-year-old girl with multiple injuries sustained in an auto accident. Thus blunt injury to the right kidney was followed 8 days later by reduced urinary output and serous chest tube drainage. Intravenous dye injection showed dye in urine and in chest tube fluid, and the macerated right kidney was removed. The right pleural effusion then cleared with further drainage. The mechanism by which urine is transferred across the intact diaphragm is thought to be lymphatic drainage.