A 24-year-old man was admitted to hospital with pneumonia. On admission he was seen to have an asymmetrical build. During treatment of the lung infiltrate his clinical condition deteriorated. On the third day he coughed up great quantities of fluid which had a urine-like smell. The concentration of creatinine in this fluid was the same as in urine. On X-ray of the thorax, a massive accumulation of pleural fluid was seen. Shortly after aspiration of 1000 ml of pleural fluid the patient died. At autopsy, an ectopic kidney was found in the left thoracic cavity. The pneumonia had caused an abscess that had broken into the pelvis of this ectopic kidney causing the loss of urine into the pleural cavity (urothorax) and 'uroptysis'. On the basis of anatomical and embryological aspects it is debatable if this case was genuine. It is in fact a duplication of a case report published in this journal in 1923 the reliability of which was never clarified. Biographical information from Professor A. Querido (1901-1983) which has since become available indicates that the case was faked by mischievous medical students preparing for their examinations. They had never imagined that the editors might actually accept it for publication. The case report of 1923 has now been retracted.