IgA subclasses in circulating immune complexes (IgA1IC), serum immunoglobulins and mesangial deposits in Berger's and Schönlein-Henoch glomerulonephritis (GN) were studied. Both IgA1IC and IgA2IC were significantly higher in Berger's and Schönlein-Henoch GN than in healthy people. In phases of clinical activity both IgAIC subclasses further increased. The IgA1/IgA2 ratio was found not to differ from controls in either groups of patients. An increase in polymeric IgA was observed in Berger's and in Schönlein-Henoch GN. Both IgA subclasses were found in mesangial deposits.