Trout infected with furunculosis were treated orally with sulfamer-azine, sulfathiazole, furacin, sulfanilamide and sulfadiazine, the rate of dosage being 5-11.5/gm./day/100 lbs. of fish. Furacin was used also by being added to the water. The mortality of infected fish was as follows: no medication, 50%; sulfamerazine, 17%; sulfathiazole, 23%; furacin in food followed by sulfanilamide, 28%; and furacin in water followed by sulfadiazine, 40%. Mortality sharply declined within a wk. with sulfamerazine, and dropped less rapidly with sulfathiazole, which, however, was definitely helpful.