The Immune Deficiency Foundation (IDF) conducted its second national survey of the treatment experiences and preferences of patients with primary immunodeficiency (PI) in 2008. A total of 1,030 patients with PI who were being treated with intravenous immunoglobulin (IVIG) therapy, or subcutaneous immunoglobulin (SCIG) therapy participated. The results of the survey continued to support the tremendous efficacy of immunoglobulin replacement therapy for patients with primary immunodeficiencies who are antibody deficient.