Reminders have been used in various settings, but failed to produce convincing evidence of benefits on patient adherence to colorectal cancer (CRC) screening. The aim of this study was to assess the effectiveness of sending general practitioners (GPs) printed reminders about CRC screening. We conducted a cluster-randomized controlled trial involving 144 GPs in the Val-de-Marne district (France), who provided care for any reason to 20 778 patients eligible for CRC screening between June 2010 and November 2011. Data were collected from the main statutory health-insurance programme and local cancer screening agency. GPs were randomly assigned in a 1 : 1 proportion to the intervention or the control group. Every 4 months, intervention-group GPs received a computer-generated printed list of patients who had not performed scheduled faecal occult blood test (FOBT) screening. The primary outcome was patient adherence to FOBT screening or exclusion from CRC screening for medical reasons. The screening adherence rate was 31.2% [95% confidence interval (CI) 30.3-32.1] in the control group and 32.9% (95% CI 32.0-33.8) in the intervention group [crude relative risk, 1.05 (95% CI 1.01-1.09), P<0.01]. This rate was not significantly different between groups by multilevel modelling accounting for clustering and confounding variables [adjusted relative risk, 1.07 (95% CI 0.95-1.20), P=0.27]. Computer-generated printed reminders sent to GPs did not significantly improve patient adherence to organized CRC screening by the FOBT.