OBJECTIVES: Recently reported rates of Medicare beneficiaries restricting prescription medication use because of cost ranges from 1.6 to 22%. A reliable estimate of prescription non-procurement due to cost and an understanding of this behavior is essential to appropriate policy development. METHODS: The 2000 Health and Retirement Study, nationally representative of Americans born before 1947, provides cross-sectional data regarding respondent insurance coverage and prescription non-procurement. All non-institutionalized, Medicare beneficiaries age 65 and older were identified. Weighted bivariate analysis and multivariate stepwise logistic regression modeling determined the association and independent predictive value of several risk factors, including total health insurance coverage, on prescription non-procurement. RESULTS: Data for 9771 respondents were identified. Prescription non-procurement due to cost was reported in 4.5%, 8.5%, and 9.8% of respondents with Medicare plus private insurance, Medicare only, and Medicare plus Medicaid, respectively. Bivariate analysis revealed similar risk factor-related trends both within and between health insurance categories. The final regression model included several significant factors (p<0.0001) predictive of non-procurement, the most notable being income, number of symptoms, and total prescription costs. In this model, prescription non-procurement was more likely to be reported in the Medicare-only population (OR: 1.47; 95% CI 1.46-1.48) and in the Medicare plus Medicaid population (OR: 1.11; 95% CI 1.10-1.12) as compared to respondents with Medicare plus private insurance coverage. CONCLUSIONS: Significantly different rates of persons who forego filling a prescription for cost reasons were observed among Medicare beneficiaries. More vulnerable groups of seniors were identified. Dual eligible Medicare/Medicaid enrollees and those with Medicare alone are more likely to restrict medication procurement due to cost.