AIM:To validate the clinical relevance of autofluores-cence imaging(AFI)endoscopy for the assessment of inflammatory ulcerative colitis(UC).METHODS:A total of 572 endoscopic images were se-lected from 42 UC patients:286 taken with white light imaging(WLI)and 286 with AFI from the same sites.WLI images were assessed for overall mucosal inflammation according to Mayo endoscopic subscore(MES),and for seven characteristic endoscopic features.Likewise,AFI photographs were scored according to relative abundance of red,green and blue color com-ponents within each image based on an RGB additive color model.WLI and AFI endoscopic scores from the same sites were compared.Histological evaluation of biopsies was according to the Riley Index.RESULTS:Relative to red(r=0.52,P<0.01)or blue(r=0.56,P<0.01)color component,the green color component of AFI(r=-0.62,P<0.01)corresponded more closely with mucosal inflammation sites.There were signif icant differences in green color components between MES-0(0.396±0.043)and MES-1(0.340± 0.035)(P<0.01),and between MES-1 and ≥ MES-2(0.318±0.037)(P<0.01).The WLI scores for “vascu-lar patterns”(r=-0.65,P<0.01),“edema”(r=-0.62,P<0.01),histology scores for “polymorphonuclear cells in the lamina propria”(r=-0.51,P<0.01)and “crypt architectural irregularities”(r=-0.51,P<0.01)showed correlation with the green color component of AFI.There were significant differences in green color components between limited(0.399± 0.042)and extensive(0.375±0.044)(P=0.014)polymorpho-nuclear cell inf iltration within MES-0.As the severity of the mucosal inflammation increased,the green color component of AFI decreased.The AFI green color com-ponent was well correlated with the characteristic en-doscopic and histological inflammatory features of UC.CONCLUSION:AFI has application in detecting inflammatory lesions,including microscopic activity in the co-lonic mucosa of UC patients,based on the green color component of images. AIM: To validate the clinical relevance of autofluorescence-cence imaging (AFI) endoscopy for the assessment of inflammatory ulcerative colitis (UC). METHODS: A total of 572 endoscopic images were se-lected from 42 UC patients: 286 taken with white light imaging (WLI) and 286 with AFI from the same sites. WLI images were assessed for overall mucosal inflammation according to Mayo endoscopic subscore (MES), and for seven characteristic endoscopic features. Liverwise, AFI photographs were scored according to relative abundance of red, green and blue color com-ponents within each image based on an RGB additive color model. WLI and AFI endoscopic scores from the same sites were compared. Histological evaluation of biopsies was according to the Riley Index .RESULTS: Relative to red (r = 0.52, P <0.01) or blue (r = 0.56, P <0.01) color component, the green color component of AFI (r = -0.62, P <0.01) were more closely associated with mucosal inflammation sites.There were signif icant differences in green color components between MES-0 (0.3 (P <0.01), and between MES-1 and MES-2 (0.318 ± 0.037) (P <0.01). The WLI scores for “vascu-lar patterns histology scores for ”polymorphonuclear cells in the lamina propria “ (r = -0.51, P <0.01), ”edema" (r = -0.62, (R = -0.51, P <0.01) showed correlation with the green color component of AFI. There were significant differences in green color components between limited (0.399 ± 0.042) and extensive (0.375 ± 0.044) (P = 0.014) polymorpho-nuclear cell infiltration within MES-O.As the severity of the mucosal inflammation increased, the green color component of AFI decreased. AFI green color com-ponent was well correlated with the characteristic en- doscopic and histological inflammatory features of UC. CONCLUSION: AFI has application in detecting inflammatory lesions, including microscopic activity in the co-lonic mucosa of UC patients, based on the green color component of images.