Objective: To investigate the effect of chromium picolinate on egg production, egg quality, serum biochemical indices and immune response. Methods: A total of 120 49 w old Beijing Red commercial layers were randomly allotted to one of five treatments, and fed a basal corn soybean meal diet and the basal diet supplemented with 0.4,2.0,10.0 or 20.0 mg/kg Cr as chromium picolinate under heat stress for 30 days.Results: Cr increased average egg weight(P0.20) on egg yield, feed intake and feed/egg ratio. Added Cr at 0.4 ,2.0,10.0 mg/kg enhanced (P

0.10)between the two Cr sources was observed in all indices studied; Cr level affected the relative weight of spleen (P