Abstract: The glucocorticoid receptor (GR) of cocks were partially blocked with 75,50,25,10 mg/kg of RU486,an antagonist,for 24 hours and 50 mg/kg of RU486 for 72 hours.The immunological changes were studied in the process.The results showed that the IL-2 and IFN inductive activities of lymphocytes,the mitogenic activities of T and B cells,the percentages of lymphocyte,ANAE＋cell,monocyte and the ratios of immune organ-to-body weight were greatly reduced (P<0.01) when the GR of chickens were blocked with 75 and 50 mg／kg of RU486.There were no significant changes in adove immune indexes when the GR of cocks were blocked whith 10 and 20 mg/kg of RU486.All the examined immune indexes were lower than those of control (P<0.01) and cocks GR-blocked with 50 mg/(kg·day) of RU486 for 72 hours.This indicated that the immune functions of immune system were closely related to the active GR concentration of immune cells in cock,and that greatly blocked GR of cock were resulted in immunossupression.Correlation analyses showed that the immune activities in cocks GR-blocked with RU486 were dose dependent.This suggested that the immune functions and active GR content in cock were positively correlated with eath other.