Objectives Inborn errors of metabolism (IEM) has a diverse spectrum and different incidence in different countries, the early diagnosis at presymptomatic stage is imperative to benefic patient from sequelae. Phenylke-tonuria (PKU) / hyperphenylalaninemia (HPA) is the most common metabolism disorder in Shanghai as well as in other regions. The study is to further clarify the incidence of inborn errors of metabolism among newborn in Shanghai. Methods The dried blood spot specimens were collected from near 90 local maternity and children’s hospitals or general hospitals in Shanghai. PKU / HPA screening was carried out by fluorometric method. Neonatal screening using tandem mass spectrometry was performed in one of the study centers, Xinhua neonatal screening center. Results A total of 815 160 cases were screened from 2001 - 2007 in Shanghai, the incidence of PKU / HPA was 1 ∶ 12 351. The tetrahydrobiopterin deficiency was 12.9% among hyperphenylalaninemia patients. According to the 116 000 neonatal samples data detected by tandem mass spectrometry, 20 cases were confirmed diagnosis, including 6 kinds diseases, it was PKU / HPA, maple syrup urine disease, methylmalonicacidemia, propionic acidemia, 3-methylcrotonyl-CoA carboxylase defection, and short chain acyl-CoA dehydrogenase deficiency. Conclusions The pilot study shown that inborn errors of metabolism neonatal screen-ing using tandem mass was 1 ∶ 5 800 in Shanghai, PKU / HPA was the most common disease. It is expected that the expansion of newborn screening using tandem mass spectrometry could be further considered and further improving inbornerrors of metabolism preventive services in Shanghai. Objectives Inborn errors of metabolism (IEM) has a diverse spectrum and different incidence in different countries, the early diagnosis at presymptomatic stage is imperative to benefic patient from sequelae. Phenylke-tonuria (PKU) / hyperphenylalaninemia (HPA) is the most common metabolism disorder in Shanghai as well as in other regions. The study is to further clarify the incidence of inborn errors of metabolism among newborn in Shanghai. Methods The dried blood spot specimens were collected from near 90 local maternity and children’s hospitals or general hospitals in Shanghai. PKU / HPA screening was carried out by fluorometric method. Neonatal screening using tandem mass spectrometry was performed in one of the study centers, Xinhua neonatal screening center. Results A total of 815 160 cases were screened from 2001 - 2007 in Shanghai, the incidence of PKU / HPA was 1: 12 351. The tetrahydrobiopterin deficiency was 12.9% among hyperphenylalaninemia patients. According to the 116 000 neonatal samples data detected by tandem mass spectrometry, 20 cases were confirmed diagnosis, including 6 kinds diseases, it was PKU / HPA, maple syrup urine disease, methylmalonicacidemia, propionic acidemia, 3-methylcrotonyl-CoA carboxylase defection, and short chain acyl- CoA dehydrogenase deficiency. Conclusions The pilot study showed that inborn errors of metabolism neonatal screen-ing using tandem mass was 1: 5 800 in Shanghai, PKU / HPA was the most common disease. It is expected that the expansion of newborn screening using tandem mass spectrometry could be further considered and further improved inbornerrors of metabolism preventive services in Shanghai.