OBJECTIVES:This study compared trends in colorectal cancer (CRC) incidence and mortality rates among Koreans in South Korea and Korean Americans and non-Hispanic whites in California between 1999 and 2009, and examined CRC screening rates and socio-demographic correlates of CRC screening in the two Korean populations. DESIGN:Age-standardized CRC incidence and mortality rates of Koreans in South Korea and Korean Americans and non-Hispanic whites in California for the years 1999-2009 were obtained from annual reports of cancer statistics and modeled using joinpoint regression. Using 2009 data from the Korean National Health and Nutrition Examination Survey and the California Health Interview Survey, we estimated and compared CRC screening rates and test modalities. We used multiple logistic regression to examine socio-demographic correlates of completion of CRC screening according to the guidelines among the two Korean populations. RESULTS:CRC incidence and mortality rates among South Koreans increased during 1999-2009 but more slowly during the late 2000s. In California, CRC incidence increased among Korean American females but decreased among non-Hispanic whites. About 37% of South Koreans and 60% of Korean Americans reported completion of CRC screening according to guidelines in 2009. Among South Koreans, married status, higher income, and private health insurance were associated with CRC screening, adjusting for other factors. Among Korean Americans, having health insurance was associated with CRC screening. CONCLUSION:Despite almost identical CRC screening guidelines in South Korea and the USA and substantially higher screening rates among Korean Americans as compared to South Koreans, disparities remain in both populations with respect to CRC statistics. Thus, efforts to promote primary and secondary prevention of CRC in both Korean populations are critically important in both countries.