OBJECTIVES: Mammography screening has been considered as an effective way for early detection of breast cancer to reduce the mortality of breast cancer. In Taiwan, mammography screening has been offered biennially free for woman aged 50-69 years since July 1, 2004. Nevertheless, the participation rate of mammography screening was quite low among women eligible for this benefit, and factors that influence beneficiaries’ decision on participation remained unknown. Thus, the study aimed to examine major determinants associated with participation in mammography screening among eligible women in Taiwan. METHODS: The Taiwan Longitudinal Health Insurance Dataset of 2005 was conducted for the study. Women aged 50-69 years on July 1, 2004 or going to be aged 50 years during July 1, 2004 to December 31, 2009 were identified as study subjects. Age, socio-demographic characteristics, previous experience of Pap test, health-related conditions were analyzed to evaluate the association with the likelihood of participation in mammography screening using Cox proportional hazard model. RESULTS: There were 106,760 beneficiaries during the observation period. Women who were with higher wage income level, being employed, receiving Pap test in last two years, with history of benign breast disease, and having higher Charlson Comorbidity Index score were significantly more likely to participate in mammography screening. Women who were older, with breast cancer history, and residing southern part of Taiwan were significantly less likely to participate in mammography screening. CONCLUSIONS: Age, socio-demographic characteristics, experience of Pap test and health-related conditions seemed to be determinants of participation in mammography screening. Trends in participation in mammography screening by determinants need to be evaluated in the future for policy makers to address the low participation rate of mammography screening among beneficiaries.