Objective: Contraceptive efficacy depends both on patient compliance and the characteristics of the method used. Efficacy rates can thus vary across different populations, particularly in women employing user-dependent methods (i.e., oral, condoms). This study measured the contraceptive failure rates in a Medicaid and a non-Medicaid population and evaluated the efficacy variance between the two groups. Methods: Monthly contraceptive-use histories were constructed for all women using data from the 2002 National Survey of Family Growth (NSFG VI). Contraceptive use was defined by first contraception method mentioned in the survey. Poly-modal use was not defined. Women were classified as Medicaid enrollees if they reported having Medicaid coverage in the 12 months prior to the survey, or reported Medicaid payment for services. The final dataset included 1208 Medicaid-enrolled women and 6435 non-Medicaid enrolled women. Pregnancy rates were calculated each month and then annualized for women using user-dependent methods (oral contraceptives [OC], condom) or non-daily methods (IUD, injected, implanted birth control). Results: Average annual contraceptive failure rates for Medicaid vs. non-Medicaid women were: oral pill - 1.15% vs 0.13% (p=0.0051); condom - 2.05% vs. 0.55% (p=0.0015); IUD - 0.52% vs. 0.16% (p=0.5156); injected or implanted - 0.27% vs. 0.13% (p=0.3940). OC failure rate was nearly 9-times higher in the Medicaid population than in the non-Medicaid population. Failures rates for IUD, injectables and implants were also higher but the differences were not statistically significant. Conclusion: Study results largely correspond to previous published estimates (i.e., Trussell, 2004). Contraception failure rates for user-dependent methods were substantially greater in a Medicaid population than those in a non-Medicaid plan. The efficacy rates of non-daily methods were not statistically different across the two populations and thus may be the more appropriate option for a Medicaid patient or other patient subpopulations shown to have compliance issues.