A rare case of primary spinal intramedullary malignant melanoma at the T6 level in a 31-year-old man is presented. The tumor was partially removed, and neuroaxis irradiation up to 50 Gy was then administered. Subsequently, systemic interferon beta (specific activity, 2.0 X 10(8) IU/mg protein) therapy (total dose, 2.2 X 10(7) units) was begun. At the completion of these therapies, immunohistochemical analysis with monoclonal antibodies against melanoma-associated antigens confirmed the presence of melanoma cells in the cerebrospinal fluid (CSF). Chemotherapy with intrathecal administration of dacarbazine (dimethyltriazenoimidazole carboxamide, DTIC) was then initiated, to avoid the dissemination of tumor cells by the CSF. Periodic cytological examination of CSF for melanoma cells revealed a marked reduction in the number of tumor cells. Pharmacokinetic study showed that the disappearance of DTIC from the CSF was biphasic, with an initial half-life of 30 minutes and a terminal half-life of 5 hours. Follow-up examination by MRI 1 year after the operation did not disclose any significant increase in size of the residual tumor. Neither recurrence nor metastasis was observed. The pertinent literature on spinal cord melanoma is reviewed, and the usefulness of MRI and intrathecal chemotherapy with DTIC is discussed.