Chronic diseases such as cancer and cardiovascular disease have a substantial impact on mortality and global disease burden. The Korean Cancer Prevention Study-II (KCPS-II) biobank was established to investigate these chronic diseases, with a particular focus on metabolic risk factors. Recently, genetic information reflecting diverse ancestries has been incorporated to support a precision medicine approach. These data can be leveraged to identify variation in causal effects among different ancestral groups, thereby informing the development of more effective, ancestry-specific treatments. From 2004 to 2013, baseline data were collected from 156,701 individuals aged 20–85 years, recruited from 18 health promotion centres across South Korea. Outcome data are routinely obtained from Statistics Korea (mortality data), the National Cancer Centre (cancer registry data), and the National Health Insurance Service (morbidity data). Additionally, new participants have been enrolled since 2022 as part of an ongoing expansion. This population-based cohort, enriched with genetic data, provides a robust foundation for research aimed at elucidating causal relationships in chronic disease.