Intestinal trichomoniasis was observed in 156 of 202 Tupaia belangeri (77.2%). The parasites were located principally in the cecum (75%) and were far less common in the proximal portion of the colon (19%) or terminal portion of the ileum (6%). Advanced trichomoniasis was associated with liquid cecal contents but not diarrhea. The trichomonads had a tendency to penetrate the mucosal epithelial layer, causing desquamation of entire crypts. They never penetrated the epithelial basement membrane and never triggered inflammatory responses. The trichomonads were characterized by three anterior flagella and one trailing flagellum that extended over the entire parasite body, connected to it by an undulating membrane. The capitulum of the straight axostyle formed a small but well defined pelta, and the stout costa had distinct banding. The parasites thereby matched the description of Tritrichomonas mobilensis.