Background/Aims: Previous reports on ulcerative colitis in Korea were mostly about clinical features at the time of diagnosis. In this study, we analyzed not only clinical features of Korean patients with ulcerative colitis at the time of diagnosis, but also clinical courses during 5 years after diagnosis. Methods: The yearly sum of monthly symptom scores (annual disease burden index, ADBI), annual symptomatic period, and clinical severity were evaluated during 5 years after diagnosis, and factors affecting the clinical courses during first year were also analyzed. Results: The averages of ADBI, symptomatic period, and the proportion of patients in remission during the first follow-up year were 5.8±4.4, 4.0±3.1 months, and 22.1%, Those were 3.7±4.1, 3.0±3.4 months, and 32.4%, during the fifth year. The average of ADBI during the second year was significantly higher in patients with high ADBI (>4) during the first year compared with that in patients with low ADBI (6.3±5.5 vs. 2.6±3.8, p<0.01). Conclusions: From these results, we can conclude that the clinical course of ulcerative colitis, assessed by ADBI and symptomatic period, tends to improve with time and the preceding clinical course is significantly correlated to subsequent course. (Korean J Gastroenterol 2001;38: 169-176)