PURPOSE: The goal of this study was to analyze the prevalence of Clonorchis sinensis infection in people living within 5 km of the Youngsan River basin, to develop an educational program to prevent the infection, and to examine the effects of the educational program. METHODS: This study employed a one group pretest-posttest design, the subjects were 384. This study was conducted from November 20, 2008 to June 16, 2009. The results were analyzed with the SPSS/WIN 18.0 program. RESULTS: Of the residents, 5.7% were infected with Clonorchis sinensis and the knowledge level about the prevention of Clonorchis sinensis was improved significantly from 9.75+/-5.12 points before the education to 15.05+/-2.43 points after the education. One of the important effects was that the willingness to eat raw fresh-water fish was reduced after the education. CONCLUSION: Based on the results of this study, a continuous research needs to be conducted on how education and knowledge level-up change people's living attitudes for the prevention of Clonorchis sinensis infection and the reduction of the infection rate in the future.