We have treated 23 children aged 6 to 15 years affected with agammaglobulinemia or severe hypogammaglobulinemia with IgG serum levels less than 100 mg/dL with IV gammaglobulin (Sandoglobulin), 150 to 300 mg/kg/3 wk for more than 3 years. The children suffered from severe and recurrent bacterial infections, mainly of the respiratory tract. They had been treated previously with IM gammaglobulin (0.8 ml/kg/3 wk), but their serum IgG values were never higher than 100 mg/dL. We compared the data of the follow-up after 3 years of treatment with IV gammaglobulin and the follow-up after 2 years course of IM gammaglobulin. Minor adverse reactions (chills, fever, abdominal pain) were observed only in some children during the first months of therapy. These data demonstrate that the number of infections or days with fever, in bed, or in hospital dramatically decreased during IV Ig therapy, while IgG serum levels increased to approximately normal values. IV Ig is a safe and effective treatment for patients with humoral immunodeficiency.