Abstract: Objective : To search for the nature medical history of carcinomation in Esophageal Squamous Severe Dysplasia (SD). Methods : the data of 158 cases which were detected in Nov 1992 and in Apr 1997 were input computer and handed by spss software. The cumulative carcinomatious rates and median carcinomatious time were analyzed,to account the nature RR of each year Refering to the first year of carcinomatous conversion rate, the whole duration of observation was 117 months. Results : The cumulative carcinomatious rate for 10 years was 81.66%, median time was 59.4 months.From first to ten years, RR( 95% CI) were as follows: RR₂(=4.25 (0.89~20.32), RR₃=3.37 (0.67 ~16.96),RR₄=6.19 (1.33~28.77), RR₅=8.36 (1.83~38.08), RR₆=9.46 (2.07~43.14), RR₇=4.15 (0.79~21.81), RR₈=2.57 (0.42~15.68), RR₉=0, RR₁₀=41.6 (9.09~190.39), respectively. Conclusion : the population with SD in esophagus is a very high risk population, the relationship between SD and early esophageal carcinoma were affinitive.