Study entry-date: First round screening of the iFOBT arm (70,000 invitees) has to be finished in years 1 and 2 of the trial while the flexible sigmoidoscopy arm (70,000 invitees) requires years 1-4 to be completed. Randomization of altogether 140,000 invitees was performed in year 1 of the trial - thus rendering the flexible sigmoidoscopy arm prone to more relevant time-dependent events between randomization and time of screening actually being offered. Therefore, primary entry-date was defined as day of real (for those attending) or suggested appointment (for non-attenders) in the screening arm as all letters of invitation stated a suggested day for appointment chosen by randomization. Primary entry date in the iFOBT arm was similarly defined as date of iFOBT sampling for those attending and date of mailing iFOBT-kits plus one week for non-compliant invitees. Randomization date was chosen as a secondary study entry date to allow comparative analysis of effects of choosing the two entry date definitions.