Hedge fund flows characterize the average opinion of hedge fund investors about managerial skill, expected performance, financial and operational risk. However, liquidity restrictions hamper the ability of investors to rapidly switch from one fund to another. In addition, capacity constraints at the fund or style level may imply that future returns decrease when more money is allocated to a given hedge fund. In this chapter, we provide a detailed overview of what are the drivers, and limitations, of hedge fund flows, how flows are related to measures of past performance, and to what extent flows are able to predict subsequent performance. We also discuss some implications of these relationships, for example in terms of incentives to fund managers.