The effect of yeast on the treatment and prevention of the cerebrocortical necrosis (CCN) induced experimentally by amprolium in lambs was investigated in this study. Nine healthy lambs (aging between 6 and 8 months, and weighing between 14 and 16 kg) were used as a material. Nine lambs were divided into 3 groups. Each group had 3 animals. Amprolium (600 mg/kg/ day) was given to induce CCN orally to all the groups during experiment by stomach tube. Yeast (2 g/kg/day) was given orally to the lambs of group 1 and 3 to treat and to prevent the CCN. The lambs of all the groups exhibited clinical findings related with CCN between 24 and 62 days of the ex-periment, except two lambs of the group 1. Serum ALT and glucose concentrations increased (p <0.05, p<0.01), and plasma thiamine concentration decreased (p <0.05, p<0.01) in all of the lambs. Meningial hyperemia, swelling and oedematous brain were observed in alt of the lambs, excluding lambs 1 and 3 in the necropsy. Histologically, ischemic neuronal changes, perivascular and perineuronal oedema and focal necrosis were determined in cerebellar cortex in all of the lambs, excluding lambs 1 and 3. The results of this study showed that using of yeast might have beneficial in the prevention of the CCN in lambs.