Objective To select the intravenous anesthetic with less effects on the erythrocyte immunity,and observe regulation of ?-endorphin on erythrocyte immunity in vivo Methods Seventy-two mice were randomly allocated to receiving intraperitoneally normal saline 0 04ml/g (group I,n=13), thiopental sodium 60mg/kg (groupⅡ,n=10),etomidate 20mg/kg (groupⅢ,n=10),etomidate -lipuro12mg/kg (groupⅣ n=9), midazolam 20mg/kg (groupⅤ,n=12),fentanyl 100?g/kg (groupⅥ,n=10) or pethidine 20mg/kg (groupⅦ,n=10) at 9 o'clock in the morning ,respectively and were administered at half dosage at 3 o'clock in the afternoon At 9 o'clock of the next day.Results Compared with those in group Ⅰ, the rosette rate of RBC-C3b receptor(RC3bRR) decreased significantly in group Ⅱ, Ⅳ,Ⅴ and Ⅶ(P