This study examined the hypothesis that global and selective inhibition are mediated by distinct mechanisms: respectively, a peripheral mechanism, indexed by heart rate slowing, and a central mechanism, indexed by cortical but not autonomic measures. Three varieties of a Go-NoGo task were presented in which the Go signal required an index finger response rapidly followed by a middle finger response. The NoGo signal required the inhibition of (a) both responses (global inhibition), (b) the middle finger response (simple selective inhibition), or (c) the index finger response of one hand and the middle finger response of the other hand (complex selective inhibition). As anticipated, global inhibition was indexed by heart rate slowing. Most importantly, heart rate slowing was also elicited by selective inhibition and was more pronounced for complex than simple selective inhibition. These findings suggest that global and selective inhibition are mediated by one rather than two mechanisms and that heart rate is sensitive to the demands placed on this inhibition mechanism.