This review outlines some of the main conclusions about the contributions of the orbitofrontal cortex to reward learning and decision making arising from functional neuroimaging studies in humans. It will be argued that human orbitofrontal cortex is involved in a number of distinct functions: signaling the affective value of stimuli as they are perceived, encoding expectations of future reward, and updating these expectations, either by making use of prediction error signals generated in the midbrain, or by using knowledge of the rules or structure of the decision problem. It will also be suggested that this region contributes to the decision making process itself, by encoding signals that inform an individual about what action to take next. Evidence for functional specialization within orbitofrontal cortex in terms of valence will also be evaluated, and the possible contributions of the orbitofrontal cortex in representing the values of actions as well as that of stimuli will be discussed. Finally, some of the outstanding questions for future neuroimaging research of orbitofrontal cortex function will be highlighted.