The article investigates the activities of one of the most dynamically developing institutions - self-regulating organizations (SROs) in the investment securities market. The mechanism of the securities market regulation in the United States and the UK is analyzed and the differences between them are defined. There are two types of SROs in the securities market of the USA: with voluntary and compulsory membership. SROs do not only develop standards and rules, but also carry out functions that are similar to the licensing of professional activity in the stock market. It is shown that in the UK since 2001 the self-regulating status of organizations in the stock market in fact has been abolished, and they have survived only as professional ass...