Physician participation in Medicaid is an important factor in the determination of access to health care for low-income individuals. This study seeks to provide insight into the factors that affect physicians' decisions to participate in the Medicaid program. As Medicaid is administered under broad federal guidelines, there is some degree of commonality between the different programs in each state and many physician and market unique factors traverse state lines. On this basis, several propositions are presented. Physician participation in Medicaid is posited to be positively associated with Medicaid reimbursement rates, the percentage of the available patient base in the Medicaid program, physician perceived autonomy and whether the physician is a foreign medical graduate. Alternately, participation decisions are proposed to be negatively associated with practice costs, competition for paying patients, the difference between the marginal revenue derived from paying patients and revenue from Medicaid patients, and board certification. This study seeks to provide a deeper understanding of the effects of changes to the Medicaid program, and suggests their likelihood of success in providing care to vulnerable populations.