Interest in the orbitofrontal cortex has grown substantially, particularly recently. Twenty years ago, only nine papers were published that contained the term orbitofrontal. In 2007, nearly 35 papers were published every month that reported on the orbitofrontal cortex. This volume is organized into several sections beginning with consideration of the defining features of the orbitofrontal cortex, including its anatomy in different species, its evolutionary ties to more primitive chemosensory processing systems, and its more recent role in general associative learning. Next include how the orbitofrontal cortex interacts with the various circuits that are critical to learning, memory, affect, and decision making, including the hippocampus, amygdala, striatum, and other prefrontal areas. The volume concludes with a focus on orbitofrontal cortex dysfunction as it pertains to aging, addiction, and neuropsychiatric disease, with the hope that ideas generated in earlier chapters might shed light on the importance of pathological changes in the orbitofrontal cortex in these disease states.