Antineoplaston (Ap), a new antitumor agent, was clinically tested for effects on malignant brain tumors. The materials were 3 cases of glioblastoma (G,B), 2 cases of anaplastic astrocytoma, 1 case of pontine glioma, 2 cases of metastatic brain tumor and 1 case of medulloblastoma. All patients underwent radiochemotherapy and surgical resection of the tumors except the cases of pontine glioma, metastatic brain tumor and anaplastic astrocytoma. For gliomas, radiochemotherapy was used with Hu-IFN-beta. Ap was administered at a dose of 7-10 g/day in combination with remission maintenance therapy of gliomas. Complete response was obtained in one anaplastic astrocytoma. Partial response was obtained in 2 cases, a pontine glioma and a metastatic brain tumor. No change was observed in 2 cases, an anaplastic astrocytoma and a multiple brain metastasis. Progression of the disease was observed in 4 cases, 3 glioblastomas and 1 medulloblastoma, which showed continuous increase in tumor size. The effects of Ap on malignant brain tumors were considered due to synergy, since it was administered with other drugs and acceleration of tumor cellular differentiation. Ap is useful as an approach to remission maintenance therapy for brain tumors.