Survey on secondary data of taeniasis/cysticercosis was carried out in Mongolia in 2002-2006. A total of 118 taeniid proglottids, a diphyllobothriid segment, and 59 serum samples from 118 taeniasis cases were collected at National Center for Communicable Diseases, Ulaanbaatar, Mongolia. In 2006, 14 serum samples were collected from local people who had histories of epileptic seizures in Selenge Province where pig husbandry was the main business. The 118 proglottids were confirmed to be Taenia saginata by mitochondrial DNA analysis using cytochrome c oxidase subunit 1 and cytochrome b genes. T. saginata taeniasis was widely distributed at least in 10 of 21 provinces. No variation in the nucleotide sequences of the two genes was observed among T. saginata isolates from Mongolia. There was no evidence of Taenia solium taeniasis/cysticercosis or Taenia asiatica taeniasis. A diphyllobothriid segment was confirmed to be Diphyllobothrium latum by mitochondrial DNA analysis.