A case of common variable immunodeficiency (CVID) who developed non-Hodgkin's lymphoma (NHL) of the rectum is reported. A 22-year-old male student in whom CVID was diagnosed at 7 years of age was referred to our department for the treatment of rectal NHL. The patient had stage IE disease confined to the rectum after clinical diagnostic procedures. He was initially treated with radiation therapy alone, but a relapse soon occurred in the paraaortic lymph nodes. He was successfully treated with CHOP-Bleo chemotherapy and supplementation with immunoglobulin preparations. He has since remained free of NHL and infectious complications for over 30 months despite his persistent immunodeficiency.