This chapter presented an overview of security firms, which primarily offer retail services to investors, and investment banking firms, which primarily offer activities and services related to corporate customers. Firms in this industry help bring new issues of debt and equity to the financial markets. In addition, this industry facilitates the trading and market making of securities after they are issued. The chapter discussed the structure of the industry and changes in the degree of concentration in firm size in the industry over the last decade. Balance sheet information that highlighted the major assets and liabilities of the firms was also analyzed.