Common variable immunodeficiency (CVID) is the second most prevalent primary immunodeficiency disorder but clinically the most important. It causes a wide spectrum of symptoms and signs affecting many systems of the body. CVID is a combination of humoral and cell-mediated deficiency, which explains not only why so many systems are affected but also why standard therapy in the form of intravenous immunoglobulin is not always effective. The gastrointestinal tract is the largest immune organ in the body, and it is therefore expected that this immunodeficiency will affect it in some way. The gastrointestinal manifestations of CVID are variable and tend to mimic known diseases, such as celiac sprue, pernicious anemia, and inflammatory bowel disease, but show significant differences on the microscopic level. Many studies continue to confirm a high prevalence of inflammatory, malignant, and infectious gastrointestinal disorders in patients with CVID. The T-cell-mediated defects of this immunodeficiency disorder are thought to be the cause of the majority of the gastrointestinal disorders in CVID and not the antibody deficiency. Therefore, intravenous immunoglobulin alone may be ineffective. Combination therapy with immunomodulators, such as azathioprine and 6-mercaptopurine, may be needed to treat these gastrointestinal manifestations of CVID.