Stroke is an infrequent but recognized complication of heroin addiction. Two heroin addicts, aged 34 and 19 years, developed ballistic movements after intravenous heroin overdose. Patient 1 presented bilateral ballism 1 week after intravenous heroin injection. Magnetic resonance imaging (MRI) showed bilateral ischemic lesions of the globus pallidus, suggesting a generalized cerebral hypoxia during the comatose state as pathogenic mechanism. Patient 2 presented an acute left hemiballismus when consciousness was restored with naloxone. MRI demonstrated an ischemic infarct in the right striatum. An embolic mechanism of stroke was suspected in this patient, considering the normal results of blood analysis, echocardiogram and cerebral arteriograms. Ballistic movements ceased after administration of haloperidol; both patients remained without abnormal movements thereafter.