Aim. Recent reports of european studies have shown some changes in incidance and prevalence of inflamatory bowel disease in south-eastern Europe. Last studies made in some regions in Croatia have shown multiple increase in incidance and prevalence of inflamatory bowel disease. The aim of this study is to determine the incidance and prevalence of ulcerative colitis and Crohn's disease in Split-Dalmatian county in period from 2006-2012 Methods. The research included patients from the Register of inflamatory bowel diseases of the Clinical department for gastroenterology and hepatology. The data were registered and followed up in the Register by all licensed gastroenerologists in the area of Split-Dalmatian county. All the patients were more than 18 years old with confirmed diagnosis of ulcerative colitis and Crohn's disease according to clearly specified criteria of ECCO. The research is an average retrospective epidemiological study. Results. During the seven-year long period from 2006-2012 there were 553 patients registered with an inflamatory bowel disease in Split-Dalmatian county. 378 (68,4%) of them with ulcerative colitis, and 175 (31,6%) patients with Crohn's disease. Annual incidence of patients with ulcerative colitis in Split-Dalmatian county from 2006-2012 was 9/105 (95% CI: 8,2-9,9) and it decreased in the period of followed up years. Annual incidence of patients with Crohn's disease was 4/10 5 (95% CI: 3,4-4,2) and didn't change through the followed up years. Incidance of ulcerative colitis with men was 1,3 times higher than with women (χ2=7,03; P=0,007), and considering Crohn's disease it was 1,75 times higher (χ2=7,08; P=0,008). There was a major increase in representation of both diseases in towns and on islands, and among population of higher education. The highest increase of representation of ulcerative colitis was found among population with onset of disease 18-30 years old and those who were 61-70 years old. The highest increase of Crohn's disease was among the age group with onset of disease 18-30. The part of those who smoke was 14% among the patients with ulcerative colitis, and 26% among those with Crohn's disease. Positive family history was present among both groups of patients equally. Conclusion. Incidance and prevalence of ulcerative colitis has been higher than in previously published studies in Croatia and they have decreased through years of research. Incidance of Crohn's disease hasn't changed through years of research, while prevalence of ulcerative colitis and Crohn's disease has increased linearly.