We studied the distribution and density of the endocrine cells in the digestive tract of Paa spinosa using immunohistochemical method (streptavidin-peroxidase method) using eight gut hormone antisera. The 5-hydroxytryptamine immunoreactive cells were distributed throughout the digestive tract with the highest density in the stomachus pyloricus, the second highest in the duodenum, fewer in the oesophagus, stomachus cardiacus and rectum. The gastrin immunoreactive cells were located mainly in the stomachus pyloricus and occasionally in different parts of the intestine. The somatostatin immunoreactive cells occured mainly in the stomach, frequently in the stomachus pyloricus, and occasionally in different parts of the intestine. The pancreatic polypeptide immunoreaetive cells were found with the highest density in the duodenum, the second highest in the stomachus cardiacus, and rarely in the rectum. No immunoreactive cells were observed with the antisera to glucagon, substance P, growth hormone and calcitonin. but there were glucagon and substance P mucosal nerve plexus throughout the digestive tract, and both with the highest density in the duodenum [Acta Zoologica Sinica 49(6): 858 - 864, 2003].