Coccidia of the genus Eimeria arc present in roost pigs raised on dirt in the United States. They are generally considered nonpathogenic in weaned pigs. Oocysts of Eimeria spinoso Henry. 1931 were observed in tissue sections and intestinal contents of a weaned male pig that died Suddenly on a farm in Iowa. Microscopically, necrotizing enteritis associated with many thick-walled coccidial oocysts was present in intestinal sections. Examination of intestinal contents demonstrated oocysts that were thick-wallcd and had small projections on the surface of the oocyst wall, characteristic of E. spinosel Henry, 1931 of swine. Twenty-five oocysts in intestinal contents measured 20.4 by 14.2 mum. No pathogenic bacteria were detected in the pig by culture methods. but lesions suggestive of salmonellosis were observed in some tissues. The specific cause of death was not determined however, E. spinosa infection was considered to have contributed to the death of this pig. The results suggest that E. spinosa may be pathogenic for pigs.