The sample size was 14 773 asymptomatic women met inclusion criteria (mean [SD] age, 51.8 (8.2). Lesions were detected in 551 women (3.7%). These included 233 malignant lesions (233/551, 42.3%), 57 high-risk lesions (10.3%) and 261 benign lesions (47.4%). The participation rate was 7.8% of the target population of women 40-69 years of age. The majority of breast cancer cases were reported in the age group 45-49 years (23.2%). The KNMSP study recall rate for 5 consecutive years was in a range of 11.9-16.5% (mean, 14.3%). The detection rate of ductal/lobular carcinoma in situ and invasive breast cancer were 2.5 and 13.6 per 1000 screened women, respectively. Invasive ductal carcinoma was the most common type. Only 4314 women followed up within 12-15 months of the first mammography for a retention rate of 29.2%.