This book explains how the self regulatory system for U.S. securities firms works with three tiers of supervision. Overseeing the whole system is the U.S. Securities and Exchange Commission, which directly supervises the self-regulatory organizations such as the New York Stock Exchange and the National Association of Securities Dealers. In turn, these self-regulatory organizations oversee the broker-dealers who conduct the daily business of buying and selling securities. The system relies heavily on the firms' internal supervisory systems to prevent violations of securities laws, since they are in the best position to track their own internal activities. Firms may be fined, or subject to even more stringent penalties, if their supervisory systems fail. This book is an in-depth examination of how this regulatory system works, the types of regulatory problems with which broker-dealer firms must deal, why some firms have more problems than others, and what the experience with the system suggests about ways of improving self regulatory systems generally.