ABSTRACT.Objective. To demonstrate the clinical characteristics, radiologic findings, and neuropathological features of tetrahydrocannabinol-related posterior fossa ischemic stroke in adolescent patients.Design. A retrospective case and chart review of 3 cases encountered at a tertiary care institution over a span of 5 years.Setting. Inpatient and intensive care hospitalization units managing children and adolescents.Subjects. Male adolescent patients with ischemic cerebellar stroke after use of marijuana.Diagnostic Investigations. Computed tomography brain scans (3 subjects), magnetic resonance imaging brain study (1 subject), cerebral arteriography (1 subject), cerebellar biopsy (1 subject), and necropsy (2 subjects).Results. Three adolescent males had similar presentations of headache, fluctuating level of consciousness or lethargy, visual disturbance, and variable ataxia after self-administration of marijuana. They developed primary cerebellar infarctions within days after the exposure that could not be attributed to supratentorial herniation syndromes and only minimally involved brainstem structures.Conclusions. Episodic marijuana use may represent a risk factor for stroke in childhood, particularly in the posterior circulation. Early recognition of the cerebellar stroke syndrome may allow prompt neurosurgical intervention, reducing morbidity. Pediatrics 2004;113:e365-e370. URL: http://www.pediatrics.org/cgi/content/full/113/4/e365; ischemic stroke, cerebral blood flow, marijuana, adolescent drug use.