['Healthy individuals performing response suppression tasks activate anterior cingulate cortex with occurrence of false alarm error responses to nontargets. Fundamental questions include whether this error-related activation provides a signal contributing to behavioral control and, given generally poorer performance on such tasks by addicts, whether this signal is disrupted in addiction.', 'We used rapid, event-related functional magnetic resonance imaging to study 13 individuals with opiate dependence and 26 healthy control individuals performing a Go/NoGo task.', 'Compared with controls, opiate addicts exhibited an attenuated anterior cingulate cortex error signal and significantly poorer task performance. In controls, the individual level of event-related anterior cingulate cortex activation accompanying false alarm error positively predicted task performance, particularly sensitivity in discriminating targets from nontargets.'] Do opiate addicts lack error-dependent activation of rostral anterior cingulate?