OBJECTIVES Non-oral contraceptives, offer greater efficacy and little potential for patient compliance error compared to user dependent products such as oral contraceptives (OC). Patient non-compliance and subsequent high failure rates are a potential problem in the US. Therefore, use of non-oral contraception with LNG-IUS (MIRENA®) maybe a cost-effective strategy for a health plan. The study objective is to compare the cost-effectiveness of LNG-IUS and oral contraceptives (OC) on prevention of pregnancy from a US payer's perspective. METHODS A Markov model was constructed to simulate cost savings associated with switching 2% of women (N=2841) requiring contraception from OC (27.5-25.5%) to LNG-IUS (4.3-6.3%). The study population was based on a 1-million member plan and included females age 18-45 who desire contraception (N=142,031). Method failure (resulting in ectopic pregnancy, spontaneous abortion, induced abortion, or birth), adverse events, and resource utilization were derived from the literature and supplemented with expert opinion when needed. Contraceptive methods costs were taken from Medi-Span Master 2007 Drug Database. Physician service and office visits costs were obtained from the average fees associated with the 2007 Procedural Terminology (CPT) codes. Both costs and effectiveness were discounted at 3% per year. Model outputs included pharmacy, medical, side effects, failure, and total costs to the health plan for a two and five year time horizon. RESULTS An increase of 2% of LNG-IUS resulted in a total cost savings of $2,146,663 (0.70%) and $8,952,120 (1.42%) from a two and five year timeframe respectively. There was a decrease in total contraception, medical, side effects and failure costs. Sensitivity analysis showed that LNG-IUS remained cost-effective up to two and six times the acquisition cost from a two and five year time horizon respectively. CONCLUSIONS This study shows that switching women from OC to LNG-IUS would offer significant savings to the health plan