The fact that internal liquidity is a key source of corporate funding puts the marginal value of cash at the center of a variety of firm decisions, including investment, payout, financing, savings, and risk management policies. The marginal value of cash is inherently a dynamic concept, because a firm facing financing frictions has to be forward-looking, managing its asset and liability structures in a unified framework and carefully trading off the use of liquidity across time and states. We present a dynamic framework for corporate liquidity management and survey the related literature, with a focus on the determinants of the marginal value of cash and its ubiquitous role in firm decisions.