This synthesis seeks to assess and explain the effectiveness of policy interventions to reduce elective wait times or lists. PubMed, EMBASE, EconLit, and grey literature were systematically searched for relevant studies and reviews. Strategies with the strongest evidence base include paying for activity, buying capacity locally and setting targets with strong incentives. There is also evidence for improving the use of existing capacity. Limiting demand through rationing can reduce waits, but is ethically problematic. Short-term injections of funding, cross-border treatment schemes, unenforced targets and promotion of private health insurance had the weakest evidence. Available evidence favours options that act fairly directly on supply, demand or local organizations' behaviour, over indirect strategies that depend on a 'domino effect'. Further research is needed to determine how to achieve major, system-wide improvements in the use of capacity.