Abstract: Some of the most sophisticated behaviors of primates, including humans, depend on the granular prefrontal cortex (PFC), yet there are few well defined and experimentally verified functional specializations within the primate PFC, especially at a causal level. Recent work from our laboratory has demonstrated contrasting specializations of the ventrolateral PFC (VLPFC) and the orbital PFC (also known as orbitofrontal cortex, OFC). We found that the OFC and the VLPFC play complementary roles in updating representations of value (i.e., valuations) that underlie decision making. Valuations represented in or accessed by the OFC depend on the dynamic internal state of an individual, what an object or action is worth at any given time based on current biological needs; valuations represented in or accessed by the VLPFC depend on dynamic external contingencies. In other words, the OFC updates valuations based on reward desirability whereas the VLPFC updates valuations based on reward availability. Additional studies have identified distinct functional subdivisions within the OFC. Its posterior part (area 13) is necessary for updating the valuations of objects and actions, while its anterior part (area 11) translates these valuations into choices and actions. According to comparative neuroanatomy, the granular parts of OFC and all of the VLPFC emerged during the evolution of primates, and it seems likely that their valuation-updating specializations elaborated on related functions performed by the agranular orbitofrontal areas that all mammals share.