We reviewed the neurologic and developmental courses in 10 children with opsoclonus-myoclonus ("dancing eyes syndrome") and neuroblastoma. All patients are alive without evidence of neoplastic disease after 8+ to 111+ months of follow-up. All had localized disease and 50% had extraabdominal tumors. Neuroblastomas of nine children had favorable Shimada histologic characteristics, and all tumors had single copies of the N-myc oncogene. After neuroblastoma resection, all patients had persistent opsoclonus-myoclonus or ataxia that responded to therapy with adrenocorticotropic hormone. Nine children had relapses of neurologic symptoms. Three years after resection, six of seven patients with sufficient follow-up were free of symptoms and had discontinued therapy. However, nine children had chronic neurologic deficits, including cognitive and motor delays, language deficits, and behavioral abnormalities. All six patients in educational programs required special assistance. Five children required physical, occupational, or speech therapy. Long-term developmental and cognitive problems should be anticipated in patients with neuroblastoma who have opsoclonus-myoclonus or ataxia or both, and early intervention should be instituted to try to minimize these deficits. (J PEDIATR 1994;125:712-6)