By using the peroxidase-antiperoxidase (PAP) immunohistochemical technique, 4 kinds of antisera raised against mammalian hormones were used for immunohistochemical identification and localization of endocrine cells in the gut of grass carp (Ctenopharyngodon idellus), black carp (Mylopharyngodon piceus), common carp (Cyprinus carpio), and culter fish (Erythroculter ilishaeformis). Positive reactions of glucagon-immunoreactive endocrine cells were proved in the whole gut of grass carp (C. idellus). There were only weak positive reactions in the foregut of common carp (C. carpio) and black carp (M. piceus). No positive reactions could be found in the gut of culter fish (E. ilishaeformis). However, only negative reactions were obtained with antisera against pepsinogen, prochymosin and neuron specific erolase in the gut of the 4 cyprinids. In the present paper, the distribution, density and morphological characteristics of glucagon-immunoreactive endocrine cells in different segments of the gut of grass carp (C. piceus) were discribed in detail. The possible physiological functions of the glucagon enter oendocrine cells were discussed and compared with those of glucagon endocrine cells in the gastrointestinal tract of herbivorous mammals.