The term "inflammatory bowel disease" includes ulcerative colitis, Leśniowski-Crohn's disease and indeterminate colitis. The history of these diseases in Poland began with Antoni Leśniowski, who in 1904 described an inflammatory tumour of the small intestine with a fistula to ascending colon. The first contemporary clinical descriptions of the main forms of inflammatory bowel disease emerged after 1960, and were made by Warsaw groups and a surgical group from Poznań. The major contributions of Polish investigators to the development of knowledge about ulcerative colitis and Leśniowski-Crohn's disease were made in the fields of immunology and genetics and in studies on kallikrein-kinin and haemostasis systems. The investigators of pathogenetic mechanisms in these diseases come from departments of gastroenterology in Warsaw, Lublin, Gdańsk and Sosnowiec.