The combination of opsoclonus, myoclonus, and ataxia in small children suggests the presence of an occult neuroblastoma, and simple laboratory tests rather than sophisticated neuroradiological procedures may point directly to that diagnosis. We described an 18-month-old boy who presented with opsomyoclonus. A small neuroblastoma arising from the left adrenal gland was found by abdominal CT scan and I-131 M. I. B. G. (Metaiodobenzylguanidine) scan. Three and a half years after tumor removal, moderate mental retardation and ataxia persisted without tumor recurrence.