Smoking, ulcerative colitis and Crohn's disease

We describe two patients with ulcerative colitis. Both had family histories of ulcerative colitis and Crohn's disease. Individual members of each family seemed to develop either Crohn's disease or ulcerative colitis according to their smoking habits. In one of these patients prolonged remission only occurred after recommencing smoking. These case reports demonstrate some of the known and postulated relationships between smoking and inflammatory bowel disease and the need for a better understanding of the underlying mechanisms.