Sixty one day old chicks were used in this experiment. Chicks were divided into three equal groups. The first group used as control. The second and third group inoculated orally with one ml containing 107 cfu of Salmonella typhimurium for three successive days. The 1st and 2nd group fed ration without probiotic, while the third group fed ration contain probiotic (1 g per kg of ration). Mortalities were recorded and examined bacteriolgically and five birds from each group were killed at 3,7, and 14 day post infection for sampling and to evaluate cecal colonization, and organ invasion by S. typhimurium. RBCs count, Hb concentration and PCV were decreased in group II. Non significant decrease in WBCs count in groupI Ion the 7 and 14 days post infection. Significant increase in lymphocytes with significant decrease in neutrophils in group II. Values of total protein and albumin showed significant decrease in group II three days post infection. Activities of ALT and AST increase in group II after two weeks of experiment Values of GGT showed no significant changes in the different groups. Urea showed significant increase in group II at 7 and 14 day post infection. The changes in the blood parameters in group III were within the range of the control group. Pathological lesions were observed in the liver and kidney of group II. Pathomorphological changes were also observed in the intestine.