Background A vast amount of literature on effects of pay-for-performance (P4P) in health care has been published. However, the evidence has become fragmented and it has become challenging to grasp the information included in it. Objectives To provide a comprehensive overview of effects of P4P in a broad sense by synthesizing findings from published systematic reviews. Methods Systematic literature search in five electronic databases for English, Spanish, and German language literature published between January 2000 and June 2011, supplemented by reference tracking and Internet searches. Two authors independently reviewed all titles, assessed articles’ eligibility for inclusion, determined a methodological quality score for each included article, and extracted relevant data. Results Twenty-two reviews contain evidence on a wide variety of effects. Findings suggest that P4P can potentially be (cost-)effective, but the evidence is not convincing; many studies failed to find an effect and there are still few studies that convincingly disentangled the P4P effect from the effect of other improvement initiatives. Inequalities among socioeconomic groups have been attenuated, but other inequalities have largely persisted. There is some evidence of unintended consequences, including spillover effects on unincentivized care. Several design features appear important in reaching desired effects. Conclusion Although data is available on a wide variety of effects, strong conclusions cannot be drawn due to a limited number of studies with strong designs. In addition, relevant evidence on particular effects may have been missed because no review has explicitly focused on these effects. More research is necessary on the relative merits of P4P and other types of incentives, as well as on the long-term impact on patient health and costs.