Numerous studies have established a role for the ACC in cognitive control. Current theories are at odds as to whether ACC itself directly engages or alternatively recruits other frontal cortical areas that implement control. The antisaccade task, in which subjects are required to make a saccade to the location opposite a suddenly appearing visual stimulus, is a simple oculomotor paradigm that has been used extensively to investigate flexible oculomotor control. Here, we tested a causal role of the dorsal ACC in cognitive control by applying electrical microstimulation during a preparatory period while monkeys performed alternating blocks of pro- and antisaccade trials. Microstimulation induced significant changes in saccadic RTs (SRTs) in both tasks. On prosaccade trials, SRTs were increased for saccades contralateral to and decreased for saccades ipsilateral to the stimulated hemisphere. In contrast, SRTs were decreased for both ipsi- and contralaterally directed antisaccades. These data show that microstimulation administered during response preparation facilitated the performance of antisaccades and are suggestive of a direct role of ACC in the implementation of cognitive control.