Norway has a long-standing tradition in twin research, but the data collected in several population-based twin studies were not coordinated centrally or easily accessible to the scientific community. In 2009, the Norwegian Twin Registry was established at the Norwegian Institute of Public Health (NIPH) in Oslo with the purpose of creating a single research resource for Norwegian twin data. As of today, the Norwegian Twin Registry contains 47,989 twins covering birth years 1895-1960 and 1967-1979; 31,440 of these twins consented to participate in health-related research. In addition, DNA from approximately 4,800 of the twins is banked at the NIPH biobank and new studies are continually adding new data to the registry. The value of the Norwegian twin data is greatly enhanced by the linkage opportunities offered by Norway's many nationwide registries, spanning a broad array of medical, demographic, and socioeconomic information.