['To evaluate the effect of combined antiretroviral therapy on serum immunoglobulin (Ig) levels in HIV-1 perinatally infected children.', 'Data from 1250 children recorded by the Italian Register for HIV Infection in Children from 1985 to 2002 were analysed. Since Ig levels physiologically vary with age, differences at different age periods were evaluated as differences in z-scores calculated using means and standard deviations of normal population for each age period. Combined antiretroviral therapy has become widespread in Italy since 1996, thus differences in Ig z-scores between the periods 1985-1995 and 1996-2002 were analysed. Data according to type of therapeutic regimen were also analysed.', 'Between the two periods 1985-1995 and 1996-2002, significant (P < 0.0001) decreases in IgG (6.29 +/- 4.72 versus 4.44 +/- 4.33), IgM (9.25 +/- 13.32 versus 5.61 +/- 7.93), and IgA (10.25 +/- 15.68 versus 6.48 +/- 11.56) z-scores, together with a parallel significant (P < 0.0001) increase in CD4 T-lymphocyte percentages, were found. These decreases were confirmed regardless of whether the children were receiving intravenous Ig or not. Ig z-scores were significantly higher in children receiving mono-therapy than in those receiving double-combined therapy (IgG, P < 0.0001; IgM, P = 0.003; IgA, P = 0.031) and in the latter children than in those receiving three or more drugs (P < 0.0001 for all z-scores). Ig z-scores correlated inversely with CD4 T-lymphocyte percentages and, directly, with viral loads.'] Does combined antiretroviral therapy reduce hyperimmunoglobulinemia in HIV-1 infected children?