To date, there is very little information regarding the pathomechanism of IgAanaphylactoid reactions and the management of affected patients. Five adultpatients with common variable immunodeficiency (CVID) and a history ofanaphylactic reactions due to the administration of immunoglobulin prepa-rations were studied. The activity of anti-IgA was determined by the gelagglutination technique using IgA-coated beads. Antibodies to IgA weredetected in the serum of all five patients. Initially, IgA ‘depleted’ intravenous(i.v.) IgG preparations were infused carefully into the patients until the activ-ity of anti-IgA was decreased significantly or became undetectable. Subse-quently, unselected i.v. IgG preparations were infused, and the activity ofanti-IgA was abolished in all cases. Intravenous IgG long-term administrationresults in tolerance induction in patients with IgA anaphylactoid reactions.This tolerance appears to be related to antibody blockage in the circulationand an inhibition of antibody production. Most importantly, IgA appears toplay an important role in the treatment of CVID. Patients with IgA anaphy-lactoid reactions can be treated safely with IgA containing i.v. IgG prepara-tions following tolerance induction.