Under the Affordable Care Act, Medicaid fees for primary care services were increased to Medicare levels from January 1, 2013 through December 31, 2014. This paper uses data from the Urban Institute’s 2014 survey of Medicaid physician fees to estimate how large a reduction in Medicaid primary care fees will occur on January 1, 2015, if the ACA’s Medicaid primary care fee bump expires. We estimate that, in the 49 states studied and in the District of Columbia, expiration of the Medicaid primary care fee bump would lead to an average 42.8 percent reduction in fees for primary care services for eligible providers.