Four studies were performed to examine peripheral factors involved with food intake regulation in the domestic fowl. In the first study, the mechanism by which tryptophan depresses food intake was clarified. Intraperitoneal injections of tryptophan methyl ester were demonstrated to inhibit feeding in Single Comb White Leghorn (SCWL) cockerels. Intragastric intubations of tryptophan inhibited food intake and decreased body temperature of SCWL cockerels. These results, in conjunction with previous findings, indicate that tryptophan's inhibitory influence on food intake is peripherally rather than centrally based. The second study explored the role of the duodenum in food intake regulation. Intraduodenal glucose loads had no effect on food intake of SCWL or Rock Cornish (RC) commercial broiler cockerels. In addition, splanchnicectomized birds did not respond to intraduodenal glucose infusions any differently than sham-operated controls. Apparently, the duodenum does not play a significant role in food intake control in the fowl. Hepatic involvement in appetite regulation was examined in SCWL and RC cockerels in the third study. Amino acid solutions failed to influence food intake when infused intraportally in either strain of chicken. Relatively small glucose or lipid solutions depressed food intake significantly when infused intraportally in the SCWL birds but had no effect in the RC cockerels. The liver appears to be integrally involved in controlling food consumption in the SCWL chicken. In the final study, the existence of a "hunger" factor in the peripheral circulation of two lines of chickens divergently selected for body weight was explored. Intrahepatic infusions of plasma from food deprived high-weight line chickens stimulated food intake of sated low-weight line chickens. These studies indicate that peripheral mechanisms are important in regulating appetite in light-breed chickens such as the SCWL, however, such mechanisms in heavy-breed chickens such as the RC appear to be less sensitive. This desensitization in heavy-breed chickens suggests that genetic selection for increased growth has affected the food intake control systems. / Ph. D.