Seventy-eightcasesofretinoblastoma(Rb)diagnosedattheEyeENTHospital,ShanghaiMedicalUniversityfrom1953to1985werestudied.Theresultsofmultiplelogisticregressionanalysisandconditionalprobabilitymodelshowedthathighfetalorderhadamoderaterisk(OR=1.28,P<0.05)ofdevelopingunilateralRb.Bothunilateralandbilateralcaseswereindependentofparentalages,andnointeractioncouldbefoundbetweenfetalorderandpaternalofmaternalage;also,theeffectoffetalorderwasnotconfoundedbyparentalages.