Event-related functional magnetic resonance imaging (erfMRI) was employed to measure the hemodynamic response during a Go/No-go task in 16 healthy subjects. The task was designed so that Go and No-go events were equally probable, allowing an unbiased comparison of cerebral activity during these two types of trials. In accordance with prediction, anterior cingulate was active during both the Go and No-go trials, dorsolateral and ventrolateral prefrontal cortex was more active during the No-go trials, while primary motor cortex, supplementary motor area, pre-motor cortex and cerebellum were more active during Go trials. These findings are consistent with the hypothesis that the anterior cingulate cortex is principally engaged in making and monitoring of decisions, while dorsolateral and ventral lateral prefrontal sites play a specific role in response inhibition.