OBJECTIVE: Heroin use has been associated with increased impulsive behaviour. This study examined the lasting effect of heroin use on impulse control in a group of ex-heroin addicts. RESEARCH DESIGN AND METHOD: Twenty-eight men, 14 ex-heroin addicts and 14 matched controls, participated in this study. The impulse control ability between the two groups was compared. Each participant was individually interviewed for demographic data and testing of their impulse control ability using the Porteus Maze Test. RESULTS: The findings indicated that the ex-heroin addicts performed significantly more poorly on the measure of impulse control than the matched controls. CONCLUSIONS: This observation suggests that the adverse effect of heroin on impulse control may be long lasting. Alternative explanations for the findings were also discussed.