The gastrointestinal tract of the endangered Julia Creek dunnart (Sminthopsis douglasi), the largest member of the genus Sminthopsis, consists of a simple, unilocular stomach and an intestine of relatively uniform calibre throughout. There is no hindgut caecum, in common with other Australian carnivorous marsupials. Brunner’s glands form a collar at the proximal end of the duodenum; they consist of simple uncoiled tubes at Day 45 of pouch life but are well differentiated at Day 60, before the young take their first solid food at Day 65–70. Rate of passage of digesta was measured in nine adult Julia Creek dunnarts on diets of minced meat with either mealworm larvae or adult crickets added, using pulse doses of the solute marker Co–EDTA and large (0.5–1.0 mm) particles of plant cell walls mordanted with Cr. Transit time (time of first appearance in the faeces) of both markers (P < 0.001) and mean retention time (the average time markers are retained in the tract) of the solute marker (P < 0.05) were shorter on the diet containing mealworms than the cricket diet. These results suggest that emptying of the stomach (the main site of digesta retention in carnivores) was delayed on the cricket diet, possibly because of longer digestion times as a result of a tougher exoskeleton. Comparison with other data suggests that total tract passage times increase among dasyurids as body size increases.