In all groups of patients--HIV, ARC, AIDS carriers--elevated serum concentration of IgG, IgA, IgM were found. In the group of HIV carriers a significant increase of the serum concentration of IgG at the 5% level was observed and of IgM at the 1% level. In patients with ARC a significant increase of IgG and IgA was found at the 5% level and of IgM at the 1% level. In patients with AIDS significantly raised IgG values at the 5% level were recorded, and of IgA and IgM at the 1% level. In IgA a permanent increase of values occurs in AIDS carriers. In the AIDS stage 86% of the patients have values higher than mean +/- SD of controls. In all three stages of HIV infection a rise of concentrations of circulating immunocomplexes was observed (p < 0.01). The highest levels were recorded in patients with AIDS. In none of the patients the presence of antinuclear antibodies was detected. The authors discuss also possible causes of hypergammaglobulinaemia in HIV infection.