This article takes stock of some of the important contributions to the study of peacekeeping (PK). Two key topics stand out: peacekeeping burden sharing and mission effectiveness. For burden sharing, the theoretical foundation is the private provision of public goods and joint products. Implications for burden sharing differ whether financial or troop contributions are being shared, with the latter driven by jointly produced country-specific benefits. Financial burden sharing can also differ between United Nations (UN)-led and non-UN-led peacekeeping operations, wherein country-specific benefits are especially important for the latter. Many articles gauge peacekeeping effectiveness by the mission's ability to maintain the peace or to protect lives for a set time period. More recently, multiple criteria are raised for evaluating peacekeeping in today's world of multifaceted peacebuilding operations.