The IgG-subclass distribution of IgG-anti-cytoplasmic autoantibodies (ACPA) was investigated. ACPA appeared in all IgG subclasses of 25 patients with Wegener's granulomatosis (WG), but at different quantities and frequencies. No IgG subclass with ACPA specificity is closer connected to activity in WG than IgG-ACPA. The data suppose a polyclonal induction of ACPA which are not directed against epitopes of polysaccharide origin most probably. Serum-IgG4 concentration was significantly elevated in WG patients (n = 25) compared to serum of healthy controls (n = 23).