The proximal duodenum of eight marsupial species, (koala, common brushtail possum, ring-tailed possum, common wombat, great grey kangaroo, parma wallaby, short-nosed bandicoot and tiger cat) were investigated immunohistochemically using 12 specific antisera for gut hormones. Several types of immunoreactive cells were seen on the intestinal villi and in crypts of these species: 9 types in the koala; 8 types in the common brushtail possum; 7 types in the common wombat; 6 types in the short-nosed bandicoot and 5 types in the ringtailed possum, great grey kangaroo, parma wallaby and tiger cat. Gastrin-, somatostatin-, motilin- and serotonin-immunoreactive cells were seen in all species examined. A few BPP-, enteroglucagon-, CCK-, secretin-, GIP- and neurotensin-immunoreactive cells were seen but only in few species. A few substance P-immunoreactive cells were detected only in the koala. Immunoreactive cells were also seen in Brunner's glands: 5 types in the parma wallaby; 3 types in the great grey kangaroo and tiger cat; 2 types in the koala and common wombat; 1 type in the short-nosed bandicoot. No immunoreactive cells were found in Brunner's glands of the common brushtail possum.