Cerebellar ataxia and opsoclonus were the initial manifestations of an associated neuroblastoma in a 20-month-old girl. Two months after the initial symptomatology, a physical examination revealed an abnormal mass palpable left to the midline. Urinary catecholamines were within normal limits. The child's neurological findings improved immediately after surgery, and steroid treatment and the follow-up on her after 2 years revealed normal general nad neurological development. The syndrome of myoclonic encephalopathy including cerebellar ataxia, myoclonus and opsoclonus, and its relationship to neuroblastoma is reviewed. Failure to recognize this association can result in delays in both diagnosis and treatment and could be fatal.