To determine the prevalence and significance of immunoglobulin A (IgA) deficiency and partial deficiency in patients with celiac disease (CD). Selective IgA deficiency is a common primary immunoglobulin deficiency and has a higher prevalence in patients with CD. The prevalence and significance of IgA deficiency and partial deficiency in patients with CD in the United States has not previously been examined. A retrospective, cohort study of 1498 adults and 317 children seen in a University Medical Center was conducted. There were 26 patients (22 adults, 4 children) with CD who were IgA deficient and 11 (9 adults, 2 children) with CD who were partially IgA deficient. The prevalence of IgA deficiency/partial deficiency was similar among adults and children (2.1% and 1.9%, respectively, P=0.99). Among adults, concomitant autoimmune disease was present in 29% of IgA-deficient/partially deficient patients versus 12% of CD patients with normal IgA levels (P=0.0081). All 4 IgA-deficient patients who had persistently positive IgG celiac serologies while adherent to a gluten-free diet and were rebiopsied had a normal repeat biopsy. Both positive tissue transglutaminase IgG and antigliadin IgG were found in these patients. Selective IgA deficiency/partial deficiency is present in 2% of CD patients at this referral center and is equally prevalent among adults and children. IgA-deficient/partially deficient adults had a higher prevalence of concomitant autoimmune disease than those without IgA deficiency. In patients who are IgA deficient, IgG serologies may be persistently elevated despite histologic recovery.