Broiler chicks (Hubbard x Hubbard) receiving 2.5 microgram of aflatoxin/g of diet and inoculated with sporulated oocysts of Eimeria acervulina gained significantly less weight than chicks receiving either aflatoxin or coccidia alone. Aflatoxin alone affected body weight more in females than males. Blood parameters, however, showed no sex-related differences to E. acervulina or aflatoxin. E. acervulina had no effect on packed cell volume, red cell number, or hemoglobin levels. Gross lesions in the intestine caused by the coccidia appeared the same with or without dietary aflatoxin. Either aflatoxin or E. acervulina alone reduced the plasma pigment. When both were present, depigmentation was greater with some strains of coccidia than with either alone. Aflatoxin alone reduced the plasma levels of cholesterol and protein. The effect of E. acervulina on cholesterol or protein, with or without aflatoxin, depended on the coccidial strain used.