Effects of glucose, insulin, and adrenaline on the feeding latent time and the ration in 3 species of fresh-water teleost fish were studied. There has been shown a significant and uniform effect of glucose (an increase of the feeding latent period, a decrease of the ration) and of adrenaline (an increase of the feeding latent period) at initial stages of exotrophia in fish. The insulin effect on the fish feeding reaction rate is not uniform: apart from a statistically significant decrease of the feeding latent period, there were recorded opposite effects.