A SMA is a portfolio of assets under the management of a professional investment firm. In the United States, the vast majority of such firms are called registered investment advisors, and operate under the regulatory auspices of the Investment Advisors Act of 1940 and the purview of the U.S. Securities and Exchange Commission (SEC). One or more portfolio managers are responsible for day-to-day investment decisions, supported by a team of analysts, operations and administrative staff. SMAs differ from pooled vehicles like mutual funds in that each portfolio is unique to a single account (hence the name). In other words, if you set up a separate account with Money Manager X, then Manager X has the discretion to make decisions for this account that may be different from decisions made for other accounts.