The study of neural mechanisms underlying emotion regulation is currently of great interest to developmental psychologists. In order to assess normative patterns and individual differences in mechanisms of emotion regulation mediated by the frontal cortices, we examined young children's event-related potentials (ERPs) across varying emotional conditions. EEG was recorded from thirteen 4--6-year-old children, who viewed on-screen pictures of angry, neutral, and happy faces while engaged in a go/no-go task. Peak medial-frontal ERPs following picture and response cue onset were compared across emotion face types and correlated with trait anxiety. As predicted, angry faces generated the largest and fastest ERPs. Source analysis indicated centromedial and right-inferior frontal sources contributing to the ERPs for angry faces. Following the response cue, ERPs were largest when responses were withheld. Finally, more anxious children showed faster ERPs for angry faces. These results are interpreted in terms of early-developing attentional mechanisms recruited to regulate anxiety.