A rare complication of massive osteolysis (disappearing bones, Gorham's disease)is presented--namely involvement and invasion of the thoracic duct by the angiomatous tissue spreading locally from involved upper thoracic vertebrae. The resultant chylothorax in our patient was investigated and the site of the lymphatic fistula established by lymphography. Operative obliteration of the chylous leak was successfully achieved and the patient has survived. A review of the literature shows this complication to have been fatal in six other cases, including Gorham's first patient.