AIM: To investigate the mutatation type and polymorphism site in the ?-L-iduronidase (IDUA) gene of Liaoning district MPS-I patients. METHODS: The mutation type and polymorphism site in the IDUA gene of Liaoning district mucopolysaccharidosis type I (MPS-I) patients were detected by PCR-SSCP and DNA sequencing. RESULTS: ① 2 new mutations: R363H, 880+g-c in the IDUA gene of Liaoning district MPS-I patients were found. ② There were 3 polymorphism sites: R105Q、L118 and A361T in the IDUA gene of Liaoning district MPS-I patients. CONCLUSIONS: The mutation type in the IDUA gene of Liaoning district MPS-I patients is different from that of other countries and districts, while the polymorphism site in the IDUA gene of Liaoning district MPS-I patients is the same as that of other countries. [