Background: Mild to severe post-transfusion adverse reactions have been reported in a proportion of immunodeficient patients receiving intravenous immunoglobulin (IVIg). Anti-IgA antibody has been proposed to be associated with development of such reactions. Objective: To assess the association between anti-IgA levels of different isotypes and adverse reactions induced in immunodeficient patients following infusion of IVIg. Methods: In this study, IgM, IgG and IgE anti-IgA antibodies were measured by an indirect ELISA method in serum samples from 31 patients with a variety of immunodeficiencies receiving IVIg and 24 normal individuals.Results: Anti-IgA antibody of all three isotypes were detectable in all sera. However, when presented as proportion of total IgA (anti –IgA/total IgA)IgG, IgE isotypes are significantly higher in patients with adverse reactions compared to those without reactions or normal subjects.Conclusion: Both IgG and IgE anti-IgA antibodies may contribute to the development and severity of adverse reactions in some patients receiving IVIg.