Summary: Factors from the social history of male psychopaths were examined in relation to their success or failure as measured by re-convictions or psychiatric hospital re-admissions 2–3 years after treatment at Henderson Hospital. From these data a weighted prediction formula was calculated and was tested out on a further cohort of patients. As a prediction instrument it was found to be reliable to a degree of significance just above the 1 per cent level. Other aspects of the subsequent career of treated patients are noted, in particular a tendency to early but often short-lived relapse and then longer standing success.