Abstract: The experiment was conducted at the faculty of agriculture University of Ain Shams-Egypt, from January to March 2008, to study the effect of different levels of chromium yeast (cr-yeast) on broiler chickens on some physiological traits. A total of 450, one-day old unsexed chickens (Cobb) strain were used. The birds were randomly allocated to five treatments with 3 replicates each. The treatments were control (T1), without supplementation, T2, T3, T4 and T5 which were supplemented with 0.5, 1, 1.5 and 2 mg cr-yeast/kg diet respectively. Chromium yeast supplementation treatments caused a significant (p<0.05) increase in plasma glucose levels, while supplemented Cr-yeast at levels of 1 (T3), 1.5 (T4), 2 (T5) mg/kg diet resulted in a significant (p<0.05) increase in total protein and globulin as compared to control group. Also supplemented 0.5 (T2) or 2 (T5) mg Cr-yeast resulted in a significant (p<0.05) reduction in total lipid in plasma, whereas cholesterol levels which were significantly (p<0.05) decreased when Cr-yeast was supplemented at levels of 1 (T3), 1.5 (T4) and 2 (T5) mg/kg diet. Although LDL was significantly (p<0.05) decreased when 1.5 (T4) or 2 (T5) mg Cr-yeast was supplemented to the diet. Lymphoid organs percentage which was not affected by dietary supplementation of Cr-yeast except spleen percentage that was significantly (p<0.05) higher in the group that was supplemented with Cr yeast .Chromium level increased in liver, muscle and plasma as levels of supplementation was increased. Protein percentage in the breast and thigh increased significantly (p<0.05) in all chromium supplementation groups as compared to the control group, while fat percentage in the breast and thigh decrease significantly (p<0.05) when chromium level increased from 1-2 mg/kg diet. It can be concluded that Cr-yeast had a beneficial effect on some of the physiological measurements of broilers under such experimental conditions.