OBJECTIVES: This study aims to overcome some of the limitations of previous studies investigating the effects of fee removal, by looking at heterogeneity of effects within countries and over time, as well as the existence of spill-over effects on groups not targeted by the policy change. METHODS: Using routine district health services data before and after recent abolitions of user charges in Zambia and Niger, we examine the effects of the policy change on the use of health services by different groups and over time, using an interrupted timeseries design. RESULTS: Removing user fees for primary health care services in rural districts in Zambia and for children over five years old in Niger increased use of services by the targeted groups. The impact of the policy change differed widely across districts, ranging from +12% and +194% in Niger to -39% and +108% in Zambia. Eighteen months after the policy change, some of these effects had been eroded. There was evidence that abolishing user fees can both have positive and negative spillover effects. CONCLUSION: These results highlight the importance of paying attention to implementation challenges and monitoring the effects of policy reforms which are often more mixed and complicated that they appear. The comparison of these reforms in two countries also sheds light on the potentially different ways in which free care can be used as a tool to improve access.