Recently, the detection of anti-neutrophil cytoplasmic antibodies (ANCA) has gained worldwide acceptance as an important additional diagnostic tool of Wegener's granulomatosis (WG). A possible pathogenic role of ANCA has been suggested by the finding that the addition of purified IgG-ANCA to healthy neutrophils in vitro causes activation of these cells. But, investigation on neutrophil functions of patients with WG has been rare. To clarify this point, peripheral neutrophil functions (adherence, chemiluminescence and chemotaxis) of patients with active WG were examined. Adherence, chemiluminescence and chemotaxis of patients with WG were significantly suppressed when compared with control subjects. The effects of ANCA positive serum on neutrophil chemiluminescence were also examined. ANCA positive serum did not affect neutrophil chemiluminescence. These results indicate that the mechanism of WG is not simply due to neutrophil activation by ANCA.