The development of lymphoma in chronic inflammatory conditions has been a topic of great interest. Studies in inflammatory bowel disease (IBD) have demonstrated conflicting results and it is often difficult to disassociate disease severity, disease duration and the risk attributable to drug exposure. Recently presented results from the very large French population based CESAME study suggest a doubling of the risk of lymphoma in patients with IBD, with the majority of cases occurring in association with immunosuppressive therapy. Similarly, a meta-analysis of previous cohort studies concluded that the risk of lymphoma is increased four-fold in patients with IBD on thiopurine treatment (azathioprine and 6-mercaptopurine) compared to those not receiving such therapy. Such analyses cannot demonstrate causation, and it is possible that an increased lymphoma risk relates to more active underlying disease rather than thiopurine therapy, an interpretation supported by results from studies in IBD patients unexposed to such treatment.