The use of genomic information in the form of polygenic scores as a predictive biomarker for common diseases has been an area of increasing interest. Methods applied in this field have evolved rapidly recently, with several methods proposed in generating these scores. An understanding of these methodological aspects is useful for considerations around implementation in clinical practice. We provide a primer for those outside the field that gives a clear, accessible account on how polygenic scores are constructed, validated and used for disease risk prediction along with an overview of their envisioned uses within health care. (By Dr. Chantal Babb de Villiers, https://jmg.bmj.com/content/early/2020/05/05/jmedgenet-2019-106763 )