Over 15 years of follow-up, screening individuals aged 50-79 at 3% risk of colorectal cancer with annual FIT or single colonoscopy reduced colorectal cancermortality by 6 per 1000 individuals. Single sigmoidoscopy and biennial FIT reduced it by 5 per 1000 individuals. Colonoscopy, sigmoidoscopy, and annual FIT reduced colorectal cancerincidence by 10, 8, and 4 per 1000 individuals, respectively. The estimated incidence reduction for biennial FIT was 1 per 1000 individuals. Serious harms were estimated to be between 3 per 1000 (biennial FIT) and 5 per 1000 individuals (colonoscopy); harms increased with older age. The absolute benefits of screening increased with increasing colorectal cancerrisk, while harms were less affected by baseline risk. Results were sensitive to the setting defined by the guideline panel. Because of uncertainty associated with modelling assumptions, we applied a GRADE rating of low certainty evidence to all estimates.