Ulcerative colitis is a chronic inflammatory disease of the colon that is characterized by abdominal pain, diarrhea, and hematochezia. It is relatively rare in Korea, but has been on the increase. The aim of this study was to review the incidence rates and clinical features of newly diagnosed ulcerative colitis in CNUH (Chonnam National University Hospital). Symptoms, disease extent and activity, and laboratory findings were retrospectively analyzed in 187 patients (42.42±16.07 years, 53.5% male) diagnosed with ulcerative colitis at the CNUH between January 1999 and March 2009. The most prevalent age was the 5th decade, and the male to female ratio was 1.15:1. The incidence rate reached a peak in the 4th decade in female patients, whereas it showed a bimodal age distribution in male patients with a first peak in the 5th decade and a second peak in the 3rd decade. The most common clinical manifestations were hematochezia and diarrhea, whereas tenesmus and constipation were more frequent in elderly patients (p<0.01, p<0.05). Disease activity was mild in 52.4%, moderate in 8.6%, and severe in 39.0%. Disease activity was more severe in female patients (p<0.05). We found a positive correlation between the severity of disease and the extent of colitis (p=0.003). We found no differences in the incidence rates or clinical features compared with other reports. However, the disease activity was more severe, especially in female patients. Smoking is generally known to have a protective effect for ulcerative colitis. Therefore, we concluded that the female patients had more severe illness because most of them were nonsmokers.