Introduction: The Danish Adoption Register was established in 1963-1964 to explore the genetic and environmental contribution to familial aggregation of schizophrenia.
Content: The register encompass information on all 14,425 non-familial adoptions of Danish children legally granted in Denmark 1924-1947. It includes name and date of birth of each adoptee and his or her biological and adoptive parents, date of transfer to adoptive parents and date of formal adoption.
Validity and coverage: The linkage to biological and adoptive parents is close to complete, even biological fathers are registered for 91.4% of the adoptees.
Conclusion: Adoption registers are a unique source allowing disentangling of genetic and familial environmental influences on traits, risk of diseases, and mortality.