At the present time the etiology of tropical sprue is undetermined. Manson-Bahr (1948) has indicated that tropical sprue must be infective since malnutrition is not observed in many patients. Frazer (1949) has suggested that an alteration in the small bowel bacterial flora could be a mechanism for impaired absorption by competitive demands for nutrition. Thus, bacterial growth in the small bowel, which is normally bacteria-free (Cregan and Hayward 1953) could possibly lead to impaired absorption by utilization of metabolites, production of antimetabolites and/or production of toxic effects on the mucosa. Since the area of active absorption of foodstuffs is greatest in the jejunum, the present study was undertaken to sample small bowel juice in that segment for bacterial growth. It was hoped that information could be obtained to allow a more definitive conclusion regarding the role of bacteria in the etiology of malabsorption in tropical sprue.