Since 2004, the National Cancer Screening Program (NCSP) for colorectal cancer has provided annualscreening by fecal immunochemical test (FIT) for individuals aged 50 years or older in the Republic ofKorea. This study was conducted to investigate trends in the participation rate of the NCSP for colorectalcancer overall and according to gender, age and health insurance type. Therefore, we analyzed participation,positivity, and follow-up rates according to these factors. Overall participation rates for the NCSP forcolorectal cancer increased from 10.5% in 2004 to 26.2% in 2009. FIT positivity rates decreased from7.9% in 2004 to 7.1% in 2009. Follow-up rates among FIT-positive participants decreased from 64.5%in 2004 to 39.4% in 2009. Although the participation rate increased each year during the study period, itremained low compared with that of other countries. The FIT positivity rate decreased, however it wasrelatively high compared with that of other countries. Intervention is essential to raise participation rates,maximize adherence to screening recommendations, and to make certain that all population subgroups reapthe benefits of screening. Also, these data suggest that structured and standardized quality improvement activity is essential to high quality for FIT in the NCSP for clorectal cancer screening in Korea.