The proven involvement of cytokines in the pathophysiology of IBD has led to the development of powerful, selective, anticytokine drugs-so-called biologics-as a therapy for IBD. Although the efficacy of infliximab, a chimeric monoclonal IgG1 antibody directed against tumor necrosis factor, is proven and the use of biologic agents is growing worldwide, there is concern about their long-term safety, which includes the risk of developing cancer. An increased risk of malignancies, particularly lymphoma, has been reported in some studies of infliximab-treated patients with IBD; however, the increased risk could be caused by the underlying chronic disease, severity of the disease, concomitant medications (e.g. conventional immunomodulators), infliximab itself, or all of these variables. At present, the data do not provide clear evidence for a causal association between infliximab and the increased cancer risk. In appropriately selected patients with severe, refractory Crohn's disease, the benefits of biologic therapy seem to outweigh the cancer risk. Multicenter, case-control studies in large populations, with a long-term follow-up are needed to define the outcome of patients with IBD treated with biologic therapies.