The Immune Deficiency Foundation (IDF) conducted a national survey of patients with primary immune deficiency diseases (PIDD) in order to determine the extent to which Medicare patients and other PIDD patients have experienced differences in treatment since January 2005 (when new Medicare reimbursement rates went into effect); whether these differences in treatment were related to insurance coverage; and whether treatment differences had adverse effects on patient health. The survey was conducted by mail during August-October, 2006, using a sample of PIDD patients from the IDF database. A total of 1,009 usable responses were received from patients with primary immune deficiency diseases—a response rate of 35%. Most of the analysis presented in this report is based upon comparisons of 255 Medicare patients and 391 private insurance patients who are currently being treated with intravenous immunoglobulin (IVIG).