Background: The trend of increasing numbers of patients with type 2 diabetes emphasizes the need for active screening of high-risk individuals and intensive lifestyle modification (LSM). Methods/design: The community-based Korean Diabetes Prevention Study (C-KDPS) is a randomized controlled clinical trial to prevent type 2 diabetes by intensive LSM using a web-based program. The two public healthcare centers in Korea are involved, and 420 subjects are being recruited for 6 months and will be followed up for 22 months. The participants are allocated randomly to intensive LSM ( 18 individual sessions for 24 weeks) and usual care ( control group). The major goals of the C-KDPS lifestyle intervention program are: 1) a minimum of 5-7% loss of initial body weight in 6 months and maintenance of this weight loss, 2) increased physical activity (>= 150 min/week of moderate intensity activity), 3) balanced healthy eating, and 4) quitting smoking and alcohol with stress management. The web-based program includes education contents, video files, visit schedules, and inter-communicable keeping track sites. Primary outcomes are the diagnoses of newly developed diabetes. A 75-g oral glucose tolerance test with hemoglobin A1c level determination and cardiovascular risk factor assessment is scheduled at 6, 12, 18, and 22 months. Discussion: Active screening of high-risk individuals and an effective LSM program are an essential prerequisite for successful diabetes prevention. We hope that our C-KDPS program can reduce the incidence of newly developed type 2 diabetes and be implemented throughout the country, merging community-based public healthcare resources and a web-based system.