BACKGROUND Cerebellar infarctions are an important cause of neurologic disease. Failure to recognize and rapidly diagnose cerebellar infarction may lead to serious morbidity and mortality due to hydrocephalus and brain stem infarction. OBJECTIVE To identify sources of preventable medical errors, the authors obtained pilot data on cerebellar ischemic strokes that were initially misdiagnosed in the emergency department. METHODS Fifteen cases of misdiagnosed cerebellar infarctions were collected, all seen, or reviewed by the authors during a five-year period. For each patient, they report the presenting symptoms, the findings on neurologic examination performed in the emergency department, specific areas of the examination not performed or documented, diagnostic testing, the follow-up course after misdiagnosis, and outcome. The different types of errors leading to misdiagnosis are categorized. RESULTS Half of the patients were younger than 50 years and presented with headache and dizziness. All patients had either incomplete or poorly documented neurologic examinations. Almost all patients had a computed tomographic scan of the head interpreted as normal, and most of these patients underwent subsequent magnetic resonance imaging showing cerebellar infarction. The initial incorrect diagnoses included migraine, toxic encephalopathy, gastritis, meningitis, myocardial infarction, and polyneuropathy. The overall mortality in this patient cohort was 40%. Among the survivors, about 50% had disabling deficits. Pitfalls leading to misdiagnosis involved the clinical evaluation, diagnostic testing, and establishing a diagnosis and disposition. CONCLUSIONS This study demonstrates how the diagnosis of cerebellar infarction can be missed or delayed in patients presenting to the emergency department.