We present evidence that a tax bill containing antitakeover provisions proposed by the U.S. House Ways and Means Committee on October 13, 1987 and approved by the Committee on October 15 was the fundamental economic event causing the greater than 10% decline in the stock market on October 14–16, which arguably triggered the October 19 crash. The bill, which eventually passed without most of the antitakeover provisions, would have limited the deductibility of interest on debt incurred to finance corporate takeovers, leveraged buyouts and recapitalizations, and imposed other restrictions on hostile takeovers.