Cues designating one of two possible tasks preceded a target requiring a discriminative button-press response. The two tasks occurred randomly so that on each trial the subject either repeated the task from the previous trial or switched to the other task. Bi-occipital (N200), parietal (P390) and fronto-central (N430) event related potentials (ERPs) to the cue stimulus were larger for switch than repeat tasks. These results suggest that both posterior and frontal cortices participate in switching. The N200, P390, and N430 may reflect perceptual (stimulus), conceptual, and response-set shifting, respectively.