We have tested the sialoganglioside monoclonal antibody Gd-2a for scintigraphic diagnostic and for immunotherapy in children with neuroblastoma stage IV. We could confirm tumor sites with Gd-2a scans in 1/2 children. Doses of 20-60 mg/m2 were administered daily for 5-10 days. 2/2 children with multiple tumor sites showed significant tumor regression. Four children, treated preventively, are still in clinical remission. One child showed tumor progression despite Gd-2a treatment. Adverse effects included itching, rashes, and pain.