This paper canvasses the trends in self-regulation and the role of self-regulation in securities markets in different parts of the world. The paper also describes the conditions in which self-regulation might be an effective element of securities markets regulation, particularly in emerging markets. Use of self-regulation and self-regulatory organizations is often recommended in emerging markets as part of a broader strategy aimed at improving the effectiveness of securities regulation and market integrity. According to the International Organization of Securities Commissions, reliance on self-regulation is an optional feature of a regulatory regime. Self-regulatory organizations may support better-regulated and more efficient capital markets, but the value of self-regulation is again being questioned in many countries. Forces such as commercialization of exchanges, development of stronger statutory regulatory authorities, consolidation of financial services industry regulatory bodies, and globalization of capital markets are affecting the scope and effectiveness of self-regulation -- and in particular the traditional role of securities exchanges as self-regulatory organizations.The paper reviews different models of self-regulation, including exchange self-regulatory organizations, member (or independent) self-regulatory organizations, and industry or dealers associations. It draws on examples of self-regulatory organizations from many markets to illustrate the degree of reliance on self-regulation, as well as the range of functions for which self-regulatory organizations are responsible, in markets around the world. Issues that are important to the effective operation of self-regulatory organizations are discussed, such as corporate governance, managing conflicts of interest, and regulatory oversight by government authorities.