The association between cancer and immunodeficiency is well established. In common variable immunodeficiency (CVI), a primary immunodeficiency disease characterized by low serum immunoglobulins and poor antibody production, we previously reported a total of 13 cancers in 11 individuals arising in continuously observed group of patients. Of the 13, 7 were NHL and 1 was a myeloma which progressed to lymphoma. We report here the histologic, immunologic, cytogenetic, and clinical features of these 8 NHL along with 3 new lymphomas which have appeared in this group (now 117 patients). From our studies, the lymphomas which have arisen in CVI share certain features with the lymphomas which appear in the childhood immunodeficient syndromes. Wiskott Aldrich Syndrome, Ataxia Telangiectasia, or severe combined immunodeficiency: they are similar in overall frequency (13%), are often B-cell in origin, and extranodal in location. However, unlike the lymphomas of the immunodeficient child, lymphomas in CVI may be more differentiated and secrete immunoglobulin. For CVI patients with stage I or II disease, as for non-Hodgkin lymphomas in general, the prognosis is good. In our group, NHL in CVI have appeared most often in females of the 5th to 7th decade and not in childhood. Cytogenetic studies in lymphomas show that cytogenic abnormalities, including chromosomal translocation, can be found in this group, but more studies will be needed to assess the frequency of these events.