OBJECTIVES The aim of the study was to determine the incidence and the main clinical data of inflammatory bowel disease in Brittany. METHODS According to EPIMAD registry's methodology, private and public gastroenterologists (n = 139) of Brittany (2836418 inhabitants) referred all patients consulting for the first time, in 1994 and 1995 with clinical symptoms compatible with inflammatory bowel disease. An interviewer practitioner completed at the gastroenterologist's consulting room a standard questionnaire for each patient. Each case was reviewed separately by four experts to assign a diagnosis of definite, probable, possible Crohn's disease, ulcerative colitis, unclassifiable chronic colitis, or acute colitis (onset of symptoms < 6 weeks). RESULTS 657 cases were recorded: 205 Crohn's disease (31%), 165 ulcerative colitis (25%) including 75 ulcerative proctitis (46%), 42 unclassifiable chronic colitis (7%), 245 acute colitis (37%). The crude mean annual incidence (per 10(5) inhabitants) based on definite and probable cases only was 2.8 for Crohn's disease and 2.9 for ulcerative colitis. The female/male ratio was 0.9 for Crohn's disease and 0.5 for ulcerative colitis. The median age at time of diagnosis was 27 for Crohn's disease and 36 for ulcerative colitis. The median time between onset of symptoms and diagnosis was equal to 3 months for Crohn's disease and ulcerative colitis. CONCLUSION In Brittany the observed incidence of ulcerative colitis is similar to that of Crohn's disease and close to that observed in northern France. The incidence of Crohn's disease is lower. However, the real incidence of inflammatory bowel disease is currently underestimated due to the large number of acute colitis requiring a follow up and the cases of Crohn's disease classified as possible not taken into account.