The pathogenesis of ulcerative colitis is complicated and both the genetic and environmental factors contribute to its development. Familial occurrence is an example indicating that both the genetic and environmental factors play some parts in the development of ulcerative colitis because family members have similar genetic characteristics and have been exposed to similar environment. Familial ulcerative colitis is observed in about 10% to 20% of patients. Most such families contain only 2 affected members and families containing more than 2 affected members are relatively rare. We experienced a case of familial ulcerative colitis in which all 4 members (both spouses and their 2 sons) were affected. They had lived together for 29 years before all 4 members were affected. The first patient was diagnosed after 14 years of cohabitation and the rest were affected 13, 14, and 15 years after the first diagnosis. We report this case with a review of literature. (Intestinal Research 2003;1:72-77)