This study was carried out to evaluate the effects of different levels of organic chromium on performance, blood metabolites and immune responses of broiler chicks. 325 one-wk-old broiler chicks (Ross 308) were randomly allocated to five dietary treatments with five replicates in a completely randomized design. Treatments included dietary levels of 0 (control), 500, 1000, 1500 and 2000 Cr from Cr-Methionine. Chicks were fed a commercial diet (cp: 21%, ME: 2900 kcal kg -1 ) for a week before experimental period. After that, birds received starter (7-21 days) and grower (21-42 days) diets. Weight gain, feed intake and feed conversion ratio were measured periodically. At the age of 10 days, birds received Newcastle disease vaccine orally. 6 and 12 days later, blood samples were collected from the wing vein of two birds per replicate. Serum antibody titers against Newcastle virus were determined by beta HI test and expressed as log 2 . Also, at 28 and 35 days of age, two birds from each pen were immunized intraperitoneally with 0.5 ml of 10% SRBC (sheep red blood cell) suspension to determine primary and secondary humoral antibody responses. 7 days after each injection, blood samples were collected from the birds to evaluate antibody titers against SRBC Antibody titers against Newcastle virus at 16 and 22 days and SRBC at 35 and 42 days were evaluated. At 22 and 42 days, blood samples were collected to investigate serum total cholesterol, HDL cholesterol and TG concentrations. At the end of experiment, two birds from each replicate were slaughtered and then Carcass, liver, heart, pancreas as well as lymphoid organs including spleen and bursa of fabrecius were weighted and expressed as a percentage of live body weight. Experimental data were analyzed as a completely randomized design by ANOVA using the GLM procedure of SAS institute. This study showed that feed intake, weight gain, feed conversion ratio, carcass traits and lymphoid organs were not affected by treatments. Antibody titers against Newcastle at 16 and 22 days showed not significant differences among treatments. SRBC titers tended to be significantly different among treatments at 35 days (P=0.0747) but significantly affected by treatments at 42 days (P 0.05) and broilers fed 1500 Cr showed the highest antibody titer. Serum total cholesterol tended to be significantly reduced by Cr supplementation at 22 days (P=0.0511) and chicks fed 1500 chromium showed the lowest total cholesterol concentrations. However cholesterol concentration was not significantly affected by chromium at 42 days. TG concentrations were significantly different between treatments at 22 days (p 0.05) and chicks fed 1500 chromium showed the lowest TG concentration. Also groups fed dietary chromium showed lower TG than control group at 42 days (P 0.05). However HDL concentrations