The incidence of inflammatory bowel diseases (Crohn’s disease and ulcerative colitis) is increasing constantly through out the world. Many aspects of their pathogenesis are still not clear, although it is known that genetic predispositions (e.g. certain gene mutations) as well as environmental factors are involved in the onset of the disease. Heme oxygenase-1 (HO-1) catalyses the enzymatic breakdown of heme into the biliverdin, which is subsequently transformed into bilirubin, ferrous ion and carbon monoxide. It has been shown to control some of the inflammatory reactions. The results of many studies suggest its dysregulated expression in the inflamed tissue. Experiments on animal models show that induction of HO-1 expression may have the beneficial effects on the course of disease and can significantly decrease its complications.