OBJECTIVES: With the passage of the Affordable Care Act and broader concerns with health care costs in the US, physicians and hospitals will be assuming more risk for the cost and quality of health care. They will be doing so through delivery reform programs, such as accountable care organizations and bundled payment programs.  While the implications of these delivery models for healthcare costs have been identified, their potential impact on patient outcomes is not well understood. This analysis sought to review how changes to payment mechanisms over the last 20 years have impacted patient outcomes in the US. METHODS: A literature review was undertaken to examine the impact that non-fee for service reimbursement has had on patient outcomes. Ninety-seven articles which compared fee-for-service to other reimbursement mechanisms in the US were identified, of which 58 reported on patient outcomes. Non fee-for-service reimbursement mechanisms considered in this analysis included bundled payments, capitated payments, prepaid plans and managed care as distinct from fee-for-service, although the exact details of remuneration under these alternative payment systems were not specified. RESULTS: Overall 62% of studies provided evidence that fee-for-service reimbursement delivered better patient outcomes. Analysis showed that non fee-for-service reimbursement may work well for younger, healthier patients, while sicker patients with multiple chronic conditions had better outcomes under traditional fee-for-service. CONCLUSIONS: This literature review provides preliminary data on the impact that risk shifting to providers may have on patient outcomes, with evidence pointing to the most vulnerable patients having inferior outcomes under non fee-for-services as compared to those in fee-for-service.  In addition, few studies considered the long-term impact of changing financial incentives on patient outcomes. As public and private payers in the United States embrace new mechanisms of payment, great care must be taken to understand the implications on patient outcomes especially among the most vulnerable.