Initial public offerings (IPOs) play a crucial role in allocating resources in market economies. Because of the enormous importance of IPOs, an understanding of how IPOs work is fundamental to an understanding of financial markets generally. Of particular interest is the puzzling existence of high initial returns to equity IPOs in the United States and other free-market economies. Audience: Designed for use by anyone wishing to perform further academic research in the area of IPOs and by those practitioners interested in IPOs as investment vehicles.