This is a study which is a compendium of parliamentary practice as it applies to oversight. Across the world, parliaments are performing their oversight role in a variety of ways. The study offers information about the wide range of tools that parliaments have at their disposal, or may wish to develop. The commonalities and differences between parliamentary tools in 88 countries are analysed and supported with a wealth of examples. The IPU sets out the broad range of oversight options from which parliaments and other interested practioners may draw inspiration in a bid to promote efficiency and effectiveness.