The patient was admitted to tuberculosis service because of pleural effusion following upper respiratory infection. All laboratory data including sputum and fluid were negative for acid fast bacilli. The character of the fluid suggested the possibility of its being of chylous nature. A number of the criteria for this diagnosis were met. In addition an analysis for fat content of the fluid was 3% and globules present stained with sudan III. confirming the diagnosis of chylothorax. Further evidence of the chylous source of the fluid was elicited by changes in % of fat content corresponding with low and high fat diets alternately. There was a history of a severe blow to the chest one month prior to the onset of the illness which suggested relationship of trauma as an etiologic factor. Recovery resulted from conservative therapy including thoracentesis.