In this study, 40 broiler chicks (Native breed x Saso) of 21 days age
were used to evaluate the effect of dry yeast (Saccharomyces cerevisiae) onbiochemical constituents and histological examination in relation to aflatoxicosis. Chicks were divided into four groups each of 10 chicks; 11t group received a standard ration and kept as normal control, 2nd group was fed the control diet contaminated with aflatoxin (AF) 81 at a level of 0.5 mg Ikg, the 3rd group received the control diet containing dry yeast at a level of 0.05% and the 4tn group received the control diet containing aflatoxin (AF) 8, at a level of 0.5 mg Ikg and dry yeast at a rate of 0.05%. This feeding program continued for 4 weeks, the obtained data revealed that the chicks kept on diet contaminated with aflatoxin (group 2) posses the lowest values of serum total protein ,albumin, globulin. cholesterol. calcium, phosphorus, iron and copper. On the other hand, group2 showed significant increase in activity of liver e"zymes, serum alanin amino transferase ( AL T), aspartate amino tansferase (AST) and gamma glutamyl transferase (GGT) and significant increase in kidney function tests (Urea, uric acid and creatinine) while chicks fed ration containing dry yeast with or without aflatoxin (group 3&4) showed a significant improvement in the values of biochemical constituents and returned it to normal control values due to the detoxifying effect of dry yeast. At the same time, there were histopathological changes occured in liver and kidney in aflatoxicated group (G2). The addition of Saccharomyces cerevisiee could eliminate the pathological action of aflatoxin in chicks.