We used indicine N-oxide to treat 46 children with malignant solid tumors: 17 with osteosarcoma, 12 with neuroblastoma, 13 with a brain tumor, and 4 with other miscellaneous tumors. The efficacy and toxicity of the drug was assessed at the dose of 2000 mg/m2/day for five consecutive days. None of the 39 patients evaluable for response achieved a complete or partial response. Hepatotoxicity was experienced by 13 patients: 11 patients developed asymptomatic elevations of transaminases, 1 patient developed hyperbilirubinemia, and 1 developed ascites. Indicine N-oxide appears to be ineffective in the treatment of osteosarcoma, neuroblastoma, and pediatric brain tumors at this dose and schedule. Because higher doses are associated with an unacceptably high incidence of severe, irreversible hepatotoxicity, we do not recommend further study of this agent in pediatric solid tumors.