The alternative minimum tax (AMT), which originally targeted high-income taxpayers, requires annual legislation to prevent it from affecting millions of middle-income individuals each year. There are two primary reasons for the AMTs broadening impact; its parameters are not indexed for inflation and the 2001-2006 tax cuts reduced regular tax liability without changing AMT liability. In 2009, four million taxpayers will pay $33.5 billion in AMT, but without congressional action that number will rise to 27 million owing $102 billion in 2010. This paper describes the AMT and provides TPCs latest estimates of AMT coverage, revenue, and distribution.