Eimeria brunetti, an intestinal coccidial parasite of poultry, caused the most severe mucosal damage when compared to E. mivati, E. necatrix, and E. maxima. The damage caused by E. brunetti was observed in the ileum and large intestine and consisted of complete villar destruction in these areas. Oocysts of E. brunetti were observed in tissue debris. E. necatrix (jejunum) enlarged isolated villi causing the lamina propria core to extrude through the villus tip. Damage to the mucosal surface is not as severe as lesions observed on the serosal surface would indicate. E. maxima (jejunum) caused epithelial sloughing and isolated patches of exposed connective tissue. Oocysts of E. maxima were observed under the surface epithelial layer. E. mivati damaged the villus tips of the duodenum and caused sloughing of the villar epithelia exposuncated and clubbed the duodenal villi. E. mivati oocysts were observed in the infected epithelia.