An experiment was designed to evaluate the effect of both strain and sex against of SRBCs antigen on live body weight, at different ages in broiler chickens. The experimental extended from June to July 2007, in order to investigate the relationship between the general immune response to SRBCS antigen on body weight traits in broiler chicks at one cycle. Two different commercial strains (ISA Hubbard and Ross 308) were used. Chicks were brooded and reared under similar environmental condition and raised on deep litter up to marketing age (7 weeks). The feed and water were provided ad libitum. Individual body weight of 500 chicks was recorded for each strain (250 per each) separately at 0, 1, 2, 3, 4, 5, 6 and 7 weeks of age. Prepared antigen (SRBC 2.5%) was injected individually in all birds with 0.13 dose at 28 day of age. Then, chickens were bled from the wing vein at 7, 14 and 21 day post- injection for anti-body (Ab) levels determination. Means of Ab . titers were 6.91 and 5.66 at 7-d post . injection in ISA Hubbard and Ross 308, respectively, with highly significantly differences (p. 0.001) between strains. While, females had higher Ab . titers than males, but the difference were not significant. On other hand, Ab - titers at 7, 14 and 21 - d post injection in both broiler strains had negative phenotypic correlations with body weight at 7- Wks of age, being . 0.049, . 0.008 and . 0.041, respectively.