AIM: To further assess of the incidence and localization of Crohns disease (CD) in a well-defined population during the 1990s and to evaluate the prevalence of CD on the 1st of January 2002.METHODS: In a retrospective population based study, all 16-90 years old citizens of Stockholm County diagnosed as having CD according to Lennard Jonescriteria between 1990 and 2001 were included.Case identification was made by using computerized inpatient and outpatient registers. Moreover private gastroenterologists were asked for possible cases. The extent of the disease and the frequency of anorectal fistulae were determined as were the ages at diagnosis.Further, the prevalence of CD on the 1st of January 2002was assessed.RESULTS: All the 1389 patients, 689 men and 700women, fulfilled the criteria for CD. The mean incidence rate for the whole period was 8.3 per 105 (95%CI 7.9-8.8). There was no difference between the genders.The mean annual incidence of the whole study period for colorectal disease and ileocecal disease, was 4.4 (95%CI 4.0-4.7) and 2.4 (95%CI 2.1-2.6) per 105, respectively.Perianal disease occurred in 13.7% (95%CI 11.9-15.7 %)of the patients. The prevalence of CD was 213 per 100000 inhabitants.CONCLUSION: The incidence of CD has markedly increased during the last decade in Stockholm County and 0.2% of the population suffers from CD. The increase is attributed to a further increase of colorectal disease, while the incidence of ileocecal disease has remained stable.