Six opossums were evaluated as a possible animal model of radiation esophagitis. In a single exposure to the esophagus, 4 animals received 60Co radiation of various doses; 2 served as controls. Pre- and postirradiation evaluations using fiberoptic endoscopy, mucosal biopsy, barium esophagography and manometry were performed. Esophagitis developed at 1 wk in irradiated animals. Opossums receiving 17.5, 20 and 22.5 Gy [gray] (1750; 2000; and 2250 rad) became anorexic 1 wk postirradiation, and abnormal motility subsequently developed. The controls and the animal receiving 15 Gy (1500 rad) remained normal. Histological changes in the irradiated opossum esophagus resembled those in humans.