From the view of cellular morphology and enzymic histochemistry, we used the pseudopod method and NBT test to measure spontaneous activation of neutrophils in vitro. The effects of anticoagulant, temperature, and sex on the percentage of spontaneously activated neutrophils were studied. The results suggest that heparin is a better anticoagulant than EDTA because EDTA because EDTA inhibits neutrophil activation; that a higher percentage of activated neutrophils can be obtained when incubated at 37 degrees C, compared with the percentage at 25 degrees C, and at 37 degrees C the highest percentage appears an hour earlier; and that females show a higher percentage of spontaneously activated neutrophils than males, and females' highest percentage appears an hour earlier than males'. These are of referential value for further studies.