The effects of intravenous anesthetics on phagocytosis of human neutrophils were observed in vitro. 1?10~6/ml of neutrophils, isolated from heparinized venous blood of healthy human,was mixed at equivalent volume with normal saline (as control), four different concentrations (clinical doses) of droperidoI, midazolam, fentanyl,etomidate or sodium hydroxybutyrate respectively. All mixtures were incubated in each of four 24-pore culture plates. The equivalent volumes of staphylococci 6～9?10~9/ml were added to these mixtures, 10 mins, 30 mins, 2hs or 24hs after incubation individually. The successive incubations lasted 45 mins,and the neutrophil phagoeytosis rate (NPR) was calculated. The results showed that NPR was correlated negatively with the concentration of each anesthetic mentioned above. but was related to its acting-duration. It is demonstrated that these intravenous anesthetics may reduce the phagoeytosis of neutrophils in a dose-related way,therefore we suggest that antibiotics or antineoplastics should be used in combination with these anesthetics during operation.