Abstract: Objective: To investigate roles of family aggregation and genetic factors of esophageal cancer (including cardia cancer) in Ci County, and compute the segregation ratio and heritability of first-degree relatives. Methods:A population based case-control study was conducted, including285 cases of esophageal cancer and 1,415 control cases. EC incidences in relatives of the patients and controls were compared byχ2 test and Heritability (h 2) was estimated using the Falconer method. Results: The results showed that the incident rate of the first-degree relatives in the patients was 12.80% , significantly higher than that in the control group (7.52% ) (χ2=44.34, P=0.000 ). EC in families did not fit the binomial distribution well, suggesting a familial aggregation ( χ2=288 .19, P<0.0001). The heritability of EC was 29.67± 4.32%. Segregation ratio was 0.1814 (95% CI was0.1574～0.2054) which is less than 0.25. It suggests that the genetic model occurring here is the polygenetic model. Conclusion:Findings suggest that the genetic factor is important in the occurrence of EC, as family aggregation exists among the EC patients in Ci County. A family history of upper gastrointestinal cancer increases the risk for EC.