Abstract: ObjectiveTo provide clues for risk factors of sudden unexplained death(SUD)in Yunnan province by describing main characteristics of the villages with cases of SUD and comparing differences bewteen case and control villages.MethodsA1B3 case-control questionnaire survey was conducted among 35 case villages and 105 control villages to compare their demographic and environmental characteristics.ResultsAnnual ave ragein come of residents in 70.0% of villages with SUD cases was less than 1067 RMB Yuan and that of for 36.7% of villages with SUD cases was less than 786 RMB Yuan.The mean distance between case villages and town hospitals was 13.6 kilometers,and that between control villages and town hospitals was 11.7 kilometers.Mines near the villages(OR=4.18,95% CI=1.05-16.64)and far away from town hospital(OR=1.25,95% CI=1.05-1.49)were associated with the increased risk of SUD.ConclusionThe main risk factors of SUD might be the geologic environment around case villages,and background factors might include far away from cities,inconvenient traffic,lower income,and worse environmental hygiene.