Enteritis induced in neonatal dogs by oral inoculation of coronavirus 1-71 was studied by virologic, histologic, histochemical, and immunofluorescent antibody methods. The enteritis, accompanied by diarrhea, developed in 4 to 7 days and was characterized by atrophy and fusion of intestinal villi and deepening of crypts, increase in cellularity of the lamina propria, flattening of epithelial cells, and discharge of goblet cells. Intra-epithelial enzyme activities generally were depressed. Specific immunofluorescent antibody reactions were present in villous epithelium of the duodenum starting on postinoculation day 2 and of the ileum on day 4. Epiehtlium of the colon showed no reaction. Virus was present in the feces for 6 to 9 days and was recovered from the small and large intestines from day 2 through day 10. The infection was not fatal and was self limiting; the diarrhea stopped between 1 and 2 weeks. The intestinal mucosa also started recovering by the end of week 1, proceeding caudally from the duodenum.