6060 Background: Breast magnetic resonance imaging (MRI) is a sensitive method of breast imaging virtually uninfluenced by breast density. Because of the improved sensitivity, breast MRI is increasingly being used for detection of breast cancer among high risk young women. However, the specificity of breast MRI is variable and costs are high. The purpose of this study was to determine if breast MRI is a cost-effective approach for the detection of breast cancer among young women at high risk. Methods: A Markov model was created to compare annual breast cancer screening over 25 years with either breast MRI or mammography among young women at high risk. Data from published studies provided probabilities for the model including sensitivity and specificity of each screening strategy. Costs were based on Medicare reimbursement rates for hospital and physician services while medication costs were obtained from the Federal Supply Scale. Utilities from the literature were applied to each health outcome in the model including a disutility for the temporary health state following breast biopsy for a false positive test result. The analysis was performed from the payer perspective with results reported in 2005 U.S. dollars. Univariate and probabilistic sensitivity analyses addressed uncertainty in all model parameters. Results: Breast MRI provided 23.287 quality-adjusted life-years (QALYs) at a cost of $30,317 while mammography provided 23.141 QALYs at a cost of $7,895 over 25 years of screening. The cost-effectiveness ratios for the two strategies were $1302 and $341, respectively. The incremental cost-effectiveness ratio of breast MRI compared to mammography was $131,376/QALY. In univariate analysis, breast MRI screening became <$50,000/QALY when the cost of the MRI was <$405. In the probabilistic sensitivity analysis, MRI screening produced a net benefit of +0.146 QALYs (95% central range: -0.825 QALYs to +1.378 QALYs). However, breast MRI screening was superior in <1%, <$50,000/QALY in 27%, >$50,000/QALY in 32%, and inferior in 41% of 10,000 probabilistic Monte Carlo simulations. Conclusions: Breast MRI provides a net benefit when compared to mammographic screening for high risk women, however, this approach does not appear to be cost-effective at this time. No significant financial relationships to disclose.