The distribution and relative frequency of occurrence of gastrointestinal endocrine cells exhibiting immunoreactivity to eleven peptides and one amine were examined immunohistochemically in the gastrointestinal mucosa of the adult honey possum which feeds almost exclusively on nectar and pollen. Seven types of endocrine cells, immunoreactive for serotonin, somatostatin, gastrin, motilin, enteroglucagon, neurotensin and gastric inhibitory peptide (GIP), were detected in the gastrointestinal mucosa of the honey possum. In the cardiac gland region, including the diverticulum, endocrine cells were very scarce, and few serotonin- and somatostatin-immunoreactive cells were identified in 4 out of 8 honey possums. Moderate numbers of serotonin- and a few somatostatin-immunoreactive cells were found in the fundic glands. In the pyloric glands, moderate numbers of gastrin-immunoreactive cells and a few serotonin- and somatostatin-immunoreactive cells were detected. Along the length of the small intestine, serotonin-immunoreactive cells were the dominant endocrine cell type but small numbers of somatostatin-, gastrin-, motilin-, enteroglucagon-, neurotensin- and GIP-immunoreactive cells, all with different distribution patterns and relative frequencies of occurrences, were also found. In the large intestine, a small number of serotonin- and enteroglucagon-immunoreactive cells were found in all animals, but a few somatostatin- and neurotensin-immunoreactive cells were detected in some animals.