Opsoclonus-myoclonus syndrome or Dancing Eye Syndrome (OMS/DES) is a rare neurological disorder of children, which associates with neuroblastoma (NB) in approximately 50% of cases. We examined sera from five patients with (OMS-NB+) and five without NB (OMS-NB-) for autoantibodies. OMS-NB- IgG bound to the surface of a NB cell line, whereas IgG from OMS-NB+ and from NB patients Without OMS/DES bound only to permeabilised. cells. Both OMS-NB+ and OMS-NB- reduced proliferation of NB cells. We also present a case report of a child with OMS/DES without NB who made a complete recovery without treatment. Serum antibodies at presentation bound to the surface and decreased NB cell proliferation but had decreased 9 weeks later when the child was asymptomatic. These results demonstrate that sera from some OMS/DES patients contain IgG antibodies that are potentially pathogenic. (c) 2008 Elsevier B.V All rights reserved.