A new conglutinin solid phase assay for the detection of immune complexes containing IgA (IgAIC) and other conglutinin tests for immune complexes containing IgG and IgM (IgGIC and IgMIC) were used in studies on 34 patients affected by Berger's GN (92 sera) and 12 affected by Henoch-Schoenlein GN (61 sera). Thirty-six patients were observed over follow-up periods of 2-43 months. Levels of IgAIC in both groups of patients were significantly higher than those in healthy people. The values obtained in patients with Henoch-Schoenlein GN were statistically higher than those obtained in patients with Berger's GN. Moreover, IgAIC were frequently found to be associated with IgGIC and/or IgMIC. In both groups of patients, the IgAIC levels were significantly correlated with the presence of signs of clinical and histological activity such as the magnitude of microscopic hematuria, a past history of macroscopic hematuria and the percentage of glomeruli with florid epithelial crescents.