This article evaluates the effects of medical malpractice reform on claiming, malpractice premiums, physician supply, and defensive medicine. We conclude that damage caps materially reduce claim frequency, payouts per claim, and total payouts. The effects of damage caps on malpractice premiums, physician supply, and defensive medicine are more modest. It is difficult to quantify the impact of reforms other than damage caps—partly because reforms are typically adopted as a package deal, and partly because of the limitations of the available data. We close by identifying three areas that would benefit from more research.