In Canada, prior to the proliferation of (Alternative Trading Systems (ATSs), a security was generally traded on a centralized exchange. As ATSs proliferate, buyers, sellers and their agents have a growing range of options when deciding where and how to execute a trade. ATSs compete with each other and with traditional exchanges by offering, among other things, different operating models, trade types and fee structures. The competition and innovation that are stimulated by the rise in multiple marketplaces also create complications. Regulators must grapple with how to regulate these electronic alternatives to traditional exchanges; registrants (brokers, dealers and advisers) must grapple with how to fulfill their duties to clients and other regulatory obligations in the face of multiple marketplaces; and investors need to be able to understand the available options and the opportunities or pitfalls that they represent.