AIM:To understand the demographic characteristics of patients in Southwestern Ontario,Canada with ulcerative colitis(UC)in order to predict disease severity. METHODS:Records from 1996 to 2001 were exam- ined to create a database of UC patients seen in the London Health Sciences Centre South Street Hospital Inflammatory Bowel Disease Clinic.To be included, patients’charts were required to have information of their disease presentation and a minimum of 5 years of follow-up.Charts were reviewed using standardized data collection forms.Disease severity was generated during the chart review process,and non-endoscopic Mayo Score criteria were collected into a composite. RESULTS:One hundred and two consecutive patients’data were entered into the database.Demographic analyses revealed that 51%of the patients were male, the mean age at diagnosis was 39 years,13.7%had a first degree relative with inflammatory bowel disease (IBD),61.8%were nonsmokers and 24.5%were ex-smokers.In 22.5%of patients the disease was limited to the rectum,in 21.6%disease was limited to the sigmoid colon,in 22.5%disease was limited to the left colon,and 32.4%of patients had pancolitis. Standard multiple regression analysis which regressed a composite of physician global assessment of disease severity,average number of bowel movements,and average amount of blood in bowel movements on year of diagnosis and age at time of diagnosis was significant,R 2=0.306,F(7,74)=4.66,P<0.01. Delay from symptoms to diagnosis of UC,gender, family history of IBD,smoking status and disease severity at the time of diagnosis didnot significantly predict the composite measure. CONCLUSION:UC severity is associated with younger age at diagnosis and year of diagnosis in a longitudinal cohort of UC patients,and may identify prognostic UC indicators. AIM: To understand the demographic characteristics of patients in Southwestern Ontario, Canada with ulcerative colitis (UC) in order to predict disease severity. METHODS: Records from 1996 to 2001 were exam- ined to create a database of UC patients seen in the London Health Sciences Center South Street Hospital Inflammatory Bowel Disease Clinic.To be included, patients’charts were required to have information of their disease presentation and a minimum of 5 years of follow-up. Challages were reviewed using standardized data collection forms. Disease severity was generated during the chart review process, and non-endoscopic Mayo Score criteria were collected into a composite. RESULTS: One hundred and two consecutive patients’data were entered into the database. Demographic analyzes revealed that 51% of the patients were male, the mean age at diagnosis was 39 years, 13.7% had a first degree relative with inflammatory bowel disease (IBD), 61.8% were nonsmokers and 24.5% were ex-smokers.In 22.5% of patients t he disease was limited to the rectum, in 21.6% disease was limited to the sigmoid colon, in 22.5% disease was limited to the left colon, and 32.4% of patients had pancolitis. Standard multiple regression analysis which regressed a composite of physician global assessment of disease severity, average number of bowel movements, and average amount of blood in bowel movements on year of diagnosis and age at time of diagnosis was significant, R 2 = 0.306, F (7,74) = 4.66, P <0.01. Delay from symptoms to diagnosis of UC, gender, family history of IBD, smoking status and disease severity at the time of diagnosis didnot significantly predict the composite measure. CONCLUSION: UC severity is associated with younger age at diagnosis and year of diagnosis in a longitudinal cohort of UC patients, and may identify prognostic UC indicators.