Levels of immune complexes (IC) were measured before treatment in 16 patients affected with classic polyarteritis nodosa (PN) or Churg Strauss Angiitis (CSA). The six patients with PN were positive for HBV markers. The others presented severe asthma. IgG containing immune complexes were measured using Raji cell assay. Normal level was 4,642 +/- 509 (mean +/- SEM). IC levels were significantly different in patients with and without HBV markers. When HBV was present, mean IC level was 7,185 +/- 2,472. In the absence of HBV markers, mean IC level was 26,462 +/- 10,796. These results confirm that systemic vasculitis is an heterogeneous group of diseases and further suggest that pathogenesis of vasculitis is different in patients with asthma and those with HBV markers.