BACKGROUND The incidence and mortality rate for cancer in patients with primary immunodeficiency diseases have increased greatly. Lymphomas constitute more than 50% of tumors identified in the Immunodeficiency Cancer Registry, but solid tumors are frequent in these patients, especially gastric carcinomas. In addition to immunologic impairment, other local conditions such as chronic atrophic gastritis with intestinal metaplasia and pernicious anemia, usually observed in these patients, may play an important role in the genesis of gastrointestinal tumors. RESULTS This report describes a 23-year-old patient with X-linked agammaglobulinemia who had previously documented chronic atrophic gastritis with intestinal metaplasia, pernicious anemia, and parasitization with Giardia lamblia in whom an adenocarcinoma of the stomach developed. CONCLUSIONS The authors believe that it may be useful to perform a periodic gastrointestinal evaluation for all patients with primary immunodeficiencies to establish early detection and treatment of these tumors.