Although no increased risk of developing lymphoproliferative disorders has been observed in population-based studies of patients with Crohn's disease, the possibility has been suggested in the subset of patients previously treated with thiopurine metabolites and suffering from concomitant Epstein–Barr virus infection. A few cases of lymphomas have occurred in patients with Crohn's disease treated with infliximab, only one of whom showed the presence of the Epstein-Barr virus genome. We here describe the case of a patient with steroid-dependent ileal Crohn's disease treated with azathioprine and a single infusion of infliximab, who developed a diffuse large B cell ileal lymphoma. Epstein-Barr virus genome was detected in the neoplastic cells by means of polymerase chain reaction. Epstein-Barr virus may be detected in the neoplastic tissues of lymphomas of patients with Crohn's disease treated with immunosuppressants and infliximab. The identification of such cases may help to define the frequency of this association and how to manage the lymphoproliferative disorder.