The individual alternative minimum tax (AMT) was originally enacted in 1969 to guarantee that high-income individuals paid at least a minimal amount of tax. Due to design flaw, however, the AMT threatens to grow from a footnote in the tax code to a major component affecting tens of millions of taxpayers every year. Absent a change in law, more than 30 million taxpayers will become subject to the AMT by 2010. This document presents and discusses updated estimates of AMT participation, revenue, and the distribution of AMT liability.