Common Variable Immunodeficiency (CVID) patients who are seropositive for anti-IgA antibodies have a predisposition for anaphylactoid reactions to intravenous immunoglobulin replacement therapy (IVIG). Among 88 CVID patients, we identified eight with IgG anti-IgA antibodies (9%). All eight completely lacked IgA (<0.0009 g/l). Five of them had a history of anaphylactoid reactions to IVIG. However, four of these five patients tolerated subcutaneous immunoglobulin replacement therapy (SCIG). To identify predisposing factors for anti-IgA antibodies and related anaphylactoid reactions, we analyzed the clinical and immunological phenotype of affected patients. All eight IgG anti-IgA-positive patients lacked IgA(+) B cells in peripheral blood. Moreover, CVID patients with retained class-switched CD27(pos) IgM(neg) IgD(neg) memory B cells (Freiburg classification group II) and total IgA deficiency seem to have an increased risk for developing anti-IgA antibodies. In seven of the eight patients, lymphoproliferation was observed (most prominently nodular lymphatic hyperplasia), two had granulomatous disease, and two showed autoimmune phenomena.