Ulcerative colitis (UC) and Crohn’s disease (CD) are described as inflammatory bowel diseases (IBD). Their development is affected by complex interactions between environmental factors, predisposing genetic factors, changes in intestinal flora and the immune system. A special role is ascribed to immunological processes, which involve both cellular and humoral mechanisms. Biological therapy is focused on different stages of the inflammatory process. It includes pro-inflammatory cytokine neutralization, use of anti- inflammatory cytokines, and inhibition of neutrophil adhesion. Antibodies against the IL-2 receptor, IL-6 receptor and against IL-12, IL-17 and IL-23 are used in biological therapy. There are also some trials regarding the use of anti-inflammatory interleukins such as recombinant IL-10 and IL-11. Nowadays many clinical trials are focused on IL-23 and IL-23R. In the future the inhibition of its activity may be a therapeutic goal in IBD. The complexity of biological therapy requires further clinical trials to show which kind of treatment is the best in long-term follow-up.