The gastrointestinal tract of a female, immature (2400 kg body mass, 6.6 m body length) southern minke whale (Balaenoptera bonaerensis) was investigated. The forestomach had a non-glandular, keratinized squamous epithelium which was separated from the fundic chamber by a clear border between a keratinized epithelium and a glandular, folded mucosa. The beginning of the duodenum consisted of the ampulla duodeni. Both cecum and colon had a smooth external appearance without sacculations or bands. Compared to phylogenetically closely related Artiodactyla, the size of the stomach complex and the intestine was short, corresponding to the carnivorous diet of cetaceans.