In a trial to assess the effects of population-based colonoscopy screening on risks of colorectal cancer (CRC), participants aged 55–64 years were randomly assigned (1:2) either to be invited to undergo a screening colonoscopy or to receive no screening. 10-year follow-up data for participants in Poland, Norway and Sweden — 28,220 were invited, of whom 42% underwent screening, and 56,365 were not invited — showed that in intention-to-screen analysis, the risk of CRC at 10 years was lower in the invited group (0.98%) than in the group assigned to no screening (1.20%). The risk reduction was 18% (risk ratio 0.82; 95% CI 0.70–0.93). The risk of death from CRC was 0.28% in the invited group and 0.31% in the group assigned to no screening (risk ratio 0.90; 95% CI 0.64–1.16). The researchers plan to release updated analysis at 15 years.