Objective To investigate the feasibility of analyzing acylcarnitine in dry filter-paper blood spots by liquid chromatography-tandem mass spectrometry(LC-MS/MS) which could be applied to detect inborn errors of metabolism in neonates.Methods We obtained filter-paper blood from 26 dead infants from a neonatal intensive care unit(NICU) between October 1,2008 and September 30,2009.Acylcarnitine and amino acid profiles were obtained with LC-MS/MS.Four infants underwent routine autopsy.The postmortem blood specimens were compared with newborn blood specimens,and with specimens obtained from older infants with metabolic disorders.Results Of all the 26 patients,5(19.2%) were diagnosed as having different kinds of diseases:3 with methylmalonic acidemia(the concentration of C3,and the ratio of C3/C16,C3/C2 increased),1 with maple syrup urine disease(the concentration of leucine and isoleucine increased),and 1 with isovaleric aci-demia(the concentration of C5 increased).Conclusions Postmortem metabolic test can explain infant deaths and provide estimates of deaths attributable to inborn errors of metabolism in NICU.LC-MS/MS is suitable for analysis of postmortem specimens and can be considered for routine application in NICU autopsy. Objective To investigate the feasibility of analyzing acylcarnitine in dry filter-paper blood spots by liquid chromatography-tandem mass spectrometry (LC-MS / MS) which could be applied to detect inborn errors of metabolism in neonates. Methods We obtained filter-paper blood from 26 dead infants from a neonatal intensive care unit (NICU) between October 1,2008 and September 30, 2009. Acylcarnitine and amino acid profiles were obtained with LC-MS / MS. Flow infants underwent routine autopsy. Postmortem blood specimens were compared with newborn blood specimens, and with specimens obtained from older infants with metabolic disorders. Results of all the 26 patients, 5 (19.2%) were diagnosed with different kinds of diseases: 3 with methylmalonic acidemia (the concentration of C3, and the ratio of C3 / C16, C3 / C2 increased), 1 with maple syrup urine disease (the concentration of leucine and isoleucine increased), and 1 with isovaleric aci-demia (the concentration of C5 increased) .Conclusions Postmortem met abolic test can can estimate infant deaths and provide estimates of deaths attributable to inborn errors of metabolism in NICU. LC-MS / MS is suitable for analysis of postmortem specimens and can be considered for routine application in NICU autopsy.