Sera from 54 children (mean age 5.8 years) with chronic hepatitis B virus (HBV) infection were investigated for the presence of immune complexes containing HBV proteins. Clinical diagnosis was established by histology and biochemical markers and included chronic persistent (36 cases) or chronic aggressive (seven) hepatitis, liver cirrhosis (six) and HBV-mediated membranous glomerulonephritis (five). Circulating immune complexes were precipitated with 2.5% polyethylene glycol and analysed by immune blot using monoclonal antibodies against S, pre-S2 glycopeptide, pre-S1 and HBe/c epitopes. All sera, including those from 11 healthy HBV-negative blood donors contained PEG-precipitable substances, but the amount of precipitate did not correlate with the presence or amount of HBV proteins. The great majority (36 out of 40) of HBeAg-positive patients contained HBs proteins in immune complexes, but no detectable HBe protein. The immune complexes usually contained more pre-S1 than the free HBsAg particles from the same patient. The precipitates of anti-HBe-positive patients rarely contained HBV proteins (two out of 14) and, if so, in low amounts. During follow up of six patients we found that high levels of HBs-containing immune complexes may be correlated with subsequent elimination of HBV. This elimination is possibly initiated by binding of anti-pre-S1 antibodies to HBV and HBs particles.