The epidemiology of inflammatory bowel disease (IBD) in southern Europe is still not well-known. Sporadic reports have suggested a lower incidence and a milder course of the disease in Italy, but conclusive data are still lacking. To shed light on this issue, we conducted a retrospective study of IBD incidence (from January 1978 to December 1987) in the metropolitan area of Florence (650,000 inhabitants). We also estimated IBD prevalence at December 31, 1987. Our study included both in-patients and out-patients referred to the Gastroenterological and Surgical Departments of the area. The diagnosis was based on well-established clinical, endoscopical, radiological, histological and surgical criteria. Overall, nine-hundred IBD patients were identified, but only 359 (195 males, 164 females) met the eligibility criteria for inclusion in the incidence study (area of residence and period of diagnosis); of these, 263 had ulcerative colitis (UC), 96 had Crohn's disease (CD), and 6 had IBD. The average incidence rate of CD was 1.5/100,000 per year while its prevalence was 17.3/100,000. The average incidence rate of UC was 4.0/100,000 per year and the prevalence was 49.6/100,000. Both the incidence and the prevalence rates for UC and CD were higher in males than in females. This retrospective, hospital-based study shows that, in this area, the incidence rate of IBD has steadily increased over the period considered. Further studies specifically focused on risk factors are needed.