Two trials were conducted with 108 pigs, 12-14 weeks old, to study the effects of feeding various levels of aflatoxin. Under the conditions of these experiments, rations containing up to 450 ppb aflatoxin B1 did not significantly affect weight gains or feed conversion of growing-finishing pigs. Rations containing 615 ppb aflatoxin B1 slightly decreased weight gains, and rations containing 810 ppb aflatoxin B1 greatly decreased weight gains and appeared to decrease feed conversion. One of the 10 pigs fed the 810 ppb aflatoxin ration died and severe liver degeneration was observed.