In 1955 Gorham and Stout described the syndrome of lymphangiomatosis of the bone resulting in widespread monofocal osteolysis in the skeletal system. The results of therapy are difficult to evaluate as the disease may come to a sudden stand-still. If angiomatosis arises near the thorax, pleural effusion occurs due to simultaneous involution of the thoracic duct. This complication has a fatal outcome and effective treatment is required. A case is reported in a 61-year-old male in whom radiotherapy of the lower ribs on the right thorax reduced the lymphangiomatous swelling and healed the chylothorax.