Inflammatory bowel disease (IBD) includes two similar yet distinct conditions called ulcerative colitis (UC) and Crohn's disease (CD). These diseases affect the digestive system and cause the inflammation of intestinal tissue, form sores and bleed easily. Most children with IBD are diagnosed in late childhood and adolescence. However, both UC and CD have been reported as early as in infancy. Most information pertaining to the epidemiology of IBD is based upon adult studies. Symptoms include abdominal pain, cramping, fatigue and diarrhea. Genetic factors play a significant role in determining IBD susceptibility. Epidemiological data support a genetic contribution to the pathogenesis of IBD. Recently, numerous new genes have been identified as being involved in the genetic susceptibility to IBD: TNF-308A, CARD15 (NOD2), MIF-173, N-acetyltransferase 2 (NAT2), NKG2D (natural killer cell 2D), STAT6 (signal transducer and activator of transcription 6), CTLA-4 (cytotoxic T lymphocyte antigen-4), MICA-MICB (major histocompatibility complex A and B), HLA-DRB1, HLA class-II, IL-18, IL-4, MICA-A5, CD14, TLR4, Fas-670, p53 and NF-kappaB. The characterization of these novel genes has the potential to identify therapeutic agents and aid clinical assessment of phenotype and prognosis in patients with IBD (UC and CD).