Until recently, scant attention has been paid to the effect of antidepressant drugs on emotion, and we have little knowledge about the way antidepressant drugs modulate neural processing of emotional and affective information, or their relationship to mood changes. Numerous behavioral studies have examined the impact of depression on the recognition of facial expressions. Although conflicting results have been obtained, depressive patients seem to attribute a different emotional valence to these stimuli than do control subjects. Recent studies have shown that a single dose of an antidepressant can increase the processing of positively versus negatively valenced material in nondepressed volunteers. Such psychopharmacological effects may ameliorate the negative biases that characterize mood disorders. Antidepressants may therefore work in a manner comparable with that of psychologic treatments that aim to redress negative biases in information processing. Studies with functional neuroimaging also show that emotional processes are dependent upon a variety of structures; most which form part of the limbic system and are altered in depression. Other studies have demonstrated changes in these structures during antidepressant treatment, mainly in the amygdala. Future research should attempt to explain, for example, the implications of changes in early emotional processing on mood and remission of depression, and the differences between acute and chronic treatment.