Abstract： Objective To explore the prenatal genetic diagnosis for classic phenylketonuria (PKU) families.Methods Probands and their family members from three classic PKU families were analyzed by combining linkage analysis through short tandem repeats (STR) polymorphism and PCR-sequencing for the exons within mutation hot spot of phenylalanine hydroxylase gene.Results Linkage analysis found uninformative for Family 1,while 100 % confirmative information was obtained from Family 2 and 3.Sequencing showed compound heterozygous mutations of phenylalanine hydroxylase gene for all of the three probands.Five mutations were detected,namely Y166X,R243Q,R413P,EX6-96A ＞ G and IVS11-1G＞ C,and IVS11-1G ＞ C was a novel identified muntation.Information from linkage analysis and mutation screening showed clearly that the fetus of Family 1 and 2 were affected,while normal for Family 3.Conclusions For those PKU families,reliable service of prenatal genetic diagnosis could be provided by combining linkage analysis with mutation screening of phenylalanine hydroxylase gene.