Abstract: Objective To evaluate the compentence of phenylalanine(Phe)and thyrotropin(TSH)measurement in neonatal screening laboratory by use of establishment of national external quality assessment(EQA)in neonatal screening laboratory.Methods National external quality assessment scheme in measurement of phenylalanine(Phe)and thyrotr opin (TSH)is established in newbom screening laboratory according to USCDC neonatal screening quality assurance program.Five dry-blood spots are distributed by EQA or ganizer to participating laboratory each time,and 3 times each year,After performing the requested tests,laboratories return their results to the EQA or ganizer,and a statistical analysis is performed to determine global and method-specific means and standard deviations of results for each analyse as well as performance assessment of individual labor ator ies.Results Twenty nine laboratories participate the EQA scheme in neonatal screening in 2001.The methods of TSH:Time-resolved immunofurometric assay(DELIA)(48.1%),average of interlabor atory coefficient of variation(CV_Inter)is 12.2%;ELISA(29.6%),CV Inter is 33.5%;fluorometr ic enzyme immunoassay(22.2%),CV_Inter is 35.9%.The methods of Phe:bacter ia inhibition assay(58.6%),V_Inter is 23.8%;fluorometric assay(41.4%),V_Inter is 15.4%.Conclusion The recommended external quality assessment is useful to find out the problems in the Phe and TSH measurement and improve the quality of neonatal screening laboratory.