The authors review the recent literature about the proinflammatory role of interleukins-1,-2,-6,-8, tumour necrosis factor and interferon-gamma in Crohn's disease and ulcerative colitis, as well as their possible use to assess disease activity and to design new therapeutic approaches. Most cytokines were secreted in excess in inflammatory bowel disease. An imbalance between interleukin-1 and interleukin-1 antagonist might be a factor responsible of the chronicity of intestinal lesions. Circulating levels of interleukin-2 receptor are related to disease activity. Preliminary data on the therapeutic use of antibodies to tumour necrosis factor are encouraging.