Even when a research synthesis shows strong, unambiguous evidence to support one course of action, 'politics' may make that review's findings less influential than well-coordinated lobbying. As Chalmers, editor of the James Lind Library, and colleagues (2002) observe: 'Research synthesis sometimes yields unwelcome results that challenge strongly held opinions and other vested interests'. Yet even if the recommendations from a research synthesis are disregarded, its very existence allows more transparency about the role of other factors in decision making. No matter how well they are done, research syntheses are not a panacea for all problems, but they do offer a valuable aid to decision making.