This investigation of the peritoneal reflections of the brush-tailed possum was carried out on eight adult specimens. The greater omentum is relatively short, whereas the lesser omentum is arranged much the same as in man. Only the mesoduodenum and the distal mesocolon are totally reflected from off the dorsal peritoneum. The remaining peritoneal folds are either free or have a weak scanty attachment to the dorsal wall thus ensuring the general mobility of the gut in an animal whose posture is both orthograde and pronograde. These reflections are discussed from a phylogenetic aspect.