The authors used indirect immunofluorescence to examine the association of antineutrophil cytoplasmic antibodies (ANCAs) with exposure to asbestos among 61 asbestos-exposed patients (mean exposure = 24.6 yr) and 39 nonexposed controls. ANCA positivity was detected significantly more frequently (p = 0.034) in the asbestos-exposed group (21.3%) than in the control group (5.1%). ANCA-associated diseases did not occur more frequently among subjects exposed previously to asbestos than among unexposed controls. These findings confirmed that exposure to asbestos is another occupational factor, as is silica exposure, that is associated with ANCA positivity. The influence of asbestos appears stronger than that of silica because ANCA positivity was found among subjects who had histories of exposure to asbestos but who did not exhibit typical radiographic signs of asbestosis on their chest x-rays. Additional stimuli may be necessary to induce systemic vasculitis in asbestos-exposed persons.