In September 2011 the Centers for Medicare and Medicaid Services awarded $85 million in grants to ten states to test financial incentive programs to encourage healthy behavior among Medicaid enrollees with chronic diseases. There is little published evidence about the effectiveness of such incentives within the Medicaid program. We evaluated the available research from three earlier Medicaid incentive programs and found mixed results. On the one hand, in Florida only about half of the $41.3 million in available credits was "claimed" by enrollees between 2006 and 2011. On the other, Idaho's incentive program was credited with improving the proportion of children who were up-to-date on well-child visits. Our findings suggest that Medicaid incentive programs should be designed so that enrollees can understand them and so that the incentives are attractive enough to motivate participation. Medicaid incentive programs also should be subject to rigorous evaluation to more clearly establish their effectiveness.