Abstract: Objective To explore the relationship beriveen birth order and primary liver cancer(PLC)，and to estin ate the relative importance of environmental and genetic factors in the developm ent of PLC.Methods Birth order analyses for PLC patients were carried out with Haldane-Smith method and Greewood-Yule method Results With Haldane-Smith method,birth order analysis for 81 LPC patients showed that the value of ∑6A_observed was 1 362 and ∑6A_expected was 1 515(t=1.89,P>0.05).With HB sAg status stratification,that values of PLC patients with HBsAg-ositive and HBsAg-negative were 2.20(P>0.05) and 0.34(P>0.00)，respectively.Results of Greenwood-Yule analysis showed that therewas no significant difference between observed distribution and expected distribution of the birth order for 81 PLC patients,with the rations of observed mumber and expected mumber fluctuation from 0.67 to 1.35,showing no linear trend of the increasing or decreasing ratios with the increasing or decreasing birth order When the data were stratified by HBsAg status,no relation was found between birth order and pathogenesis of PLC in the patients of HBsAg(-).But in the patients of HBsAg(+)，the birth order had relation with pathogenesis of PLC.Conclusion The development of PLC in the patient of HBsAg(-)was not associated with the birth order in Shunde,Guangdong.But in the patients of HBsAg(+)，birth order had relation with pathogenesis of PLC.