Objective To investigate the localization and distribution of the five endocrine cells in the digestive tract mucosa of ricefield eel(Monopterus albus). Methods Using immunocytochemical technique of strept avidin-biotin-peroxidase complex(SABC) were used. Results At least 5 kinds of immunoreactive endocrine cells distributed in the digestive tract mucosa of M.albus. They were gastrin(Gas),somatostatin(Som),5-hydroxytryptamine(5-HT),insulin(Ins),and neurofilament (NF) immunoreactive endocrine(IRE) cells.Gas and Som-IRE cells distributed between stratified squamous epithelium and goblet cell in esophagus. A large number of Gas-IRE cells were found between gastric fundus epithelium and gastric glands, and only a few in the carcia. Ins, 5-HT and NF-IRE cells distributed in the epithelium pylorus and pyloric glandular tube respectively. No any immunoreactive positive reaction was found in the gut of M.albus.In addition, immunoreactive positive reaction of glucagons was not found in whole digestive tract.All immunoreactive endocrine cells were dark brown in color.Their morphology was irregular, cytoplasmic process was shorter and thicker, their nucleus showed an empty bubble.They distributed between esophageal epithelium and gastric epithelium or glandular epithelium, and cytoplasmic process extended to the gastric lumen and glandular cavity.Conclusion There is a complex endocrine function of the digestive system in ricefield eel (M.albus) at the lowest vertebrate.