Recent studies that have examined neural correlates of action monitoring with event-related potentials (ERPs) have focused on the error-related negativity (ERN) and error positivity (Pe) on error trials, as well as the correct response negativity (CRN) on correct trials. Moreover, the ERN has been assessed in relation to a number of personality traits and psychiatric disorders. However, no study to date has assessed the reliability of the ERN, Pe, and CRN. We measured these ERPs in 45 undergraduates at baseline and 2 weeks later. For split-half and test-retest reliabilities, both the intersubject stability and score agreement were high for the ERN, CRN, and Pe. These data demonstrate excellent reliability of ERPs elicited during response monitoring, and further suggest that these ERPs are well-suited to assess trait characteristics and individual differences.