Lynch syndrome (LS) is a genetic condition that increases risk of some cancers. Typically, cancer risk in LS is estimated using individuals with an individual or family history of cancer. This may upwardly bias estimates. We estimated cancer risk in LS using a population-based cohort not selected on history of cancer. These estimates were generally consistent with published estimates, supporting use of preventative treatment in LS diagnosed incidentally through genetic sequencing. However, endometrial cancer risk was not elevated in those with LS-causing variants in the PMS2 gene. The effectiveness of endometrial cancer prevention in this group should be studied further. (By Eilidh Fummey, https://jmg.bmj.com/content/61/9/861 )