Background and Aim: The diagnosis of ulcerative colitis (UC) has been facilitated by the introduction of high resolution endoscopic imaging. Additionally, endoscopy is the most convenient and objective method for assessing and quantifying intestinal mucosal damage. However, it has been reported that there is inter-observer variation, and variation depending on the observer's experience level in the endoscopic assessment of UC. The aim of this study was to evaluate the correlation between White light imaging (WLI) and Autofluorescence imaging (AFI) pictures for endoscopic findings of ulcerative colitis. Method: We performed colonoscopy examinations in 30 patients with UC using a CF-FH260AZL/I (Olympus Inc., Tokyo Japan) and observed the same sites with WLI and AFI. A total of 408 endoscopic pictures, 204 each with WLI and AFI of the same sites were selected. WLI pictures were assessed for overall mucosal inflammation using Matts endoscopic score and seven endoscopic features: ‘vascular pattern’, ‘erythema’, ‘edema’, ‘granularity’, ‘erosions’, ‘ulcerations’ and ‘friability’, scored from 0 to 10 points. AFI pictures were scored for the rate of red, green and blue color components based on the RGB color model. Endoscopic scores of the same sites assessed with WLI and AFI were compared. These images could be downloaded from the server in JPEG format with no loss of quality. The file size of the downloaded image was about 100 kilobytes, with a pixel array of 640 × 480 and 24-bit color. Results: The rate of green color component was more closely correlated with overall mucosal inflammation (r=-0.58) than red (r=0.48) and blue (r=0.52) color components. The mean (SD) components of green color were: Matts grade (MG) 1 0.365 (0.030), MG2 0.343 (0.039), MG3 0.327 (0.039) and MG4 0.300 (0.045). The values of green components were significantly different between MG1 and MG2, and between MG2 and MG3 (p<0.05). The correlations of ‘vascular pattern’(r=-0.59) and ‘edema’ (r=-0.55) scores on WLI were high with green components on AFI, but low with ‘ulcerations’(r=-0.20). Colonic mucosa appearing as almost normal on WLI appeared as a green color on AFI, and mucosa appearing as a decreased vascular pattern and as edema on WLI appeared as a gray color, with decreased green components on AFI. Severe mucosal inflammation on WLI appeared as a deep gray (dark magenta) color on AFI, which may lead to decreased autofluorescence in the lesion. Conclusions: We conclude that AFI is a useful and objective method for the detection of inflammatory regions and the degree of inflammatory change, which is manifested by green color in the colonic mucosa in UC.