Abstract 1. 1. The taste responses from the isolated barbel of the catfish, Parasilurus asotus Linné, were studied electrophysiologically, using single fiber techniques and the electronic summator. 2. 2. The majority of single fibers in the barbels responded to hydrochloric acid and salt, but not to sucrose and quinine. The pattern of relative effectiveness of these substances differed from fiber to fiber and no classification of fiber types was clear. 3. 3. The pattern of effectiveness of monovalent salts, NH 4Cl, NaCl and LiCl, also varied from fiber to fiber. 4. 4. Potassium chloride and calcium chloride of 0·25-1·0 M caused irreversible change in the taste responses. Urethane and cocaine also abolished the taste response.