In recent years, new concepts have been formulated for the therapeutic management of the intractable forms of Crohn's disease and ulcerative colitis, the two major forms of inflammatory bowel disease. These advances are based largely on new insights into the immune-inflammatory events occurring in the gut of these patients. Analysis of the types of immune response ongoing in the inflamed intestine has revealed that in Crohn's disease there is predominantly a T-helper cell type 1 response, with exaggerated production of interleukin (IL)-12 and interferon (IFN)-gamma, whereas in ulcerative colitis the lesion seems more of an antibody-mediated hypersensitivity reaction. Despite these differences, downstream inflammatory events are the same in both conditions. In both Crohn's disease and ulcerative colitis mucosa, IL-1gamma, IL-6, IL-8 and tumour necrosis factor (TNF)-alpha are produced in excess, and the production of free radicals accompanying the influx of nonspecific inflammatory cells into the mucosa is above the normal range. Strategies aimed at inhibiting T-cell responses are therefore more relevant in Crohn's disease, whereas, in theory at least, inhibition of downstream inflammatory processes should be therapeutic in both Crohn's disease and ulcerative colitis. This review seeks to summarize studies in which anticytokine antibodies, cytokines or cytokine-modifying agents have been used in the treatment of either Crohn's disease or ulcerative colitis.