The transport and localization of vibrational energy in molecules mediate a variety of molecular processes. A central motivation for the study of vibrational energy flow in molecules has long been its influence on spectroscopy [1-11], chemical reaction kinetics in gas and condensed phases [12-30], and the desire to control chemical reactions with lasers [31-37]. In large molecules, quantum mechanical effects can both enhance as well as impose severe limitations on energy flow. The former takes place by classically forbidden tunneling processes. The latter occurs when quantum mechanical coherence effects introduce localization in a system that exhibits transport in the classical limit. In many-dimensional systems such as molecules, both of these quantum properties play a key role in energy flow, and both are addressed in this chapter.