A chemotherapeutic composition comprising a chemotherapeutic agent incorporated into a synthetic polymeric matrix releasing the chemotherapeutic by diffusion or degradation over a period of at least eight hours in an amount effective to treat brain tumors, wherein the chemotherapeutic agent is selected from the group consisting of carboplatinum, adriamycin, ternozolamide, vincristine, etoposide, cytokines, DNA or RNA including oligonucleotides, ribozymes, and guide sequences for ribozymes which inhibit translation or transciption of essential tumor genes, and dacarbazine.