Exchange-traded funds (ETFs) revolutionized asset markets by using an innovative structure to make investing in a wide variety of asset classes simpler and cheaper. With their growing importance has come increasing concern that these products pose new risks to market stability and performance. This paper examines whether ETFs affect systemic risks in financial markets and, if they do, what the mechanism is by which this impact occurs and what can be done to keep the risks under control. We review current research and empirical evidence on these issues and discuss some emerging risks in ETFs. We ask whether we have the right “rules of the road” to deal with the new drivers of market behavior.