This paper discusses a distinct cardiovascular pattern that is common to a wide variety of abused substances. The pattern consists of tachycardia that appears mediated by withdrawal of vagal inhibition, as indicated by decreases in cardiac vagal tone. This decrease in vagal tone was particularly robust with i.v. cocaine given to experienced cocaine abusers in a residential research setting. Following 40 mg i.v. cocaine, heart rate increased by approximately 30 beats/min at the same time that vagal tone decreased by approximately 2 log units. The theoretical significance of these findings is based on evidence that the results reflect a common factor among many abused drugs, but not the few aversive drugs that have been studied in this paradigm.