Because the gastrointestinal tract is the largest lymphoid organ in the body, it is not surprising that patients with immunodeficiency would present with pathological conditions in the intestine. Several studies have documented a high prevalence of inflammatory, malignant, and infectious gastrointestinal (GI) disorders in patients with common variable immunodeficiency or immunoglobulin A (IgA) deficiency. Interestingly, it has become increasingly apparent that antibody deficiency alone does not result in GI disease. Rather, defects in cellular immunity appear to predispose to a sprue-like disorder, pernicious anemia, giardiasis, nodular lymphoid hyperplasia, and even inflammatory bowel disease. In patients with unusual inflammatory GI disorders, measurement of serum immunoglobulins should be obtained.