A female of 31 with chyloascites and bilateral chylothorax is presented. The thoracic duct was obstructed below the diaphragm. The lymph vessels in the left iliac and para-aortic areas were enlarged and there were lymphocysts. When the lymph loss was greatest the patient was in a state of grave malnutrition with marked hypoalbuminaemia and an absolute and relative lymphocytopenia in the blood. "Malignant" cells were demonstrated in the chylous fluid, but no malignancy could be found at laparotomy. It is possible that the cells were confused with immature lymphocytes. The lymphatic cysts were excised and the lymph vessels ligated. Decortication of the right lung was performed. The patient recovered. The follow up time has been over four years.