Inflammatory bowel diseases (IBD) are a group of chronic gastrointestinal disorders with alternating relapses and remissions. Two main types within IBD can be distinguished: Crohn's disease and ulcerative colitis. Considering the epidemiological, immunological and genetic data, it was concluded that IBD possess multifactorial etiology, where genetic and environmental factors form the immunological background for the disease. In this review we discuss the most important genes and their protein products in IBD etiology and their impact on IBD pharmacotherapy.