Introduction: The Copenhagen School Health Records Register is an electronic register of health examination information on 372,636 children who attended school in Copenhagen, Denmark from 1936 to 2005. Content: The register contains serial measurements of height and weight as well as birth weight from 1942 onwards. Through unique personal identification numbers, linkages are possible to national registers and population studies. Validity and coverage: Measurements were recorded in the health records with precision. Virtually every schoolchild is included in the register. Conclusion: The unique qualities of the size, population-based nature and linkage possibilities of the cohort make it an invaluable resource for research.