We investigated the neural correlates of expressed vocal affect in patients with social phobia. A group of 36 patients performed an anxiogenic public-speaking task while regional cerebral blood flow (rCBF) was assessed using oxygen-15 positron emission tomography. The patients' speech was recorded and content masked using low-pass filtering (which obscures linguistic content but preserves nonverbal affective cues). The content-masked speech samples were then evaluated with regard to their level of vocally expressed nervousness. We hypothesized that activity in prefrontal and subcortical brain areas previously implicated in emotion regulation would be associated with the degree of expressed vocal affect. Regression analyses accordingly revealed significant negative correlations between expressed vocal affect and rCBF in inferior frontal gyrus, putamen, and hippocampus. Further, functional connectivity was revealed between inferior frontal gyrus and (a) anterior cingulate cortex and (b) amygdala and basal ganglia. We suggest that brain areas important for emotion regulation may also form part of a network associated with the modulation of affective prosody in social phobia.