Objective:To explore the natural history of severe dysplasia/carcinoma in situ (SD/CIS) patients and to evaluate the efficacy of endoscopic treatment to SD/CIS patients.Methods:Between January 2005 and December 2009,a population-based prospective screening program on esophageal squamous cell carcinoma (ESCC) was performed in Linzhou,China,with endoscopic screening plus iodine staining.All the eligible histologically confirmed SD/CIS patients were followed up through the door-todoor follow-up and local cancer registry.The endpoint was diagnosed as ESCC or the December 31st,2016.Kaplan-Meier survival analysis and Log-rank test were used to compare the survival rates among treated and untreated patients.Results:A total of 175 SD/CIS patients were enrolled and grouped by whether they received endoscopic treatment.Eleven-year cumulative incidence rates for untreated and treated SD/CIS patients were 10.7％ [95％ confidence interval (95％ CI):6.9-16.1] and 3.2％ (95％ CI:1.4-7.0),respectively.The ESCC incidence free survival rate,and all-cause incidence and mortality free survival rates were all significantly higher in the treated patients vs.untreated patients (P=0.043,P=0.008 and P=0.015,respectively).The ESCC mortality free survival rate showed no significant differences between the two groups (P=0.847).Conclusions:The cumulative incidence rate of SD/CIS patients to ESCC was much lower than previously reported.The Kaplan-Meier survival analysis showed that endoscopic treatment could increase the ESCC and allcause disease-free survival rates of SD/CIS patients significantly.