We examined in vitro the effect of G-CSF and temperature on superoxide (O2-) generation by Cypridina luciferin analog (CLA) dependent chemiluminescence. PMN significantly generated O2- at the concentration of G-CSF 25 ng/ml or more at 37 degrees C within the range of 0.1 from 1,000 ng/ml. O2- generation from PMN was remarkably enhanced, stimulated by opsonized zymosan (OZ) and phorbol myristate acetate (PMA), at 41 degrees C as compared with 37 degrees C. O2- generation was enhanced with the addition of 25 ng/ml of G-CSF at 41 degrees C as compared to without it at 41 degrees C. A significant enhancement of O2- generation from PMN was observed at 25 ng/ml G-CSF and 41 degrees C.