A synthetic, biodegradable wafer containing the agent carmustine with antineoplastic activity. Used to deliver drug directly into a brain tumor site and typically implanted post-surgically, the wafer is made of a biodegradable poly-anhydride copolymer and contains the nitrosourea carmustine. As an antineoplastic nitrosourea, carmustine alkylates and cross-links DNA during all phases of the cell cycle, resulting in disruption of DNA function, cell cycle arrest, and apoptosis. Carmustine also carbamoylates proteins, including DNA repair enzymes, resulting in an enhanced cytotoxic effect. Carmustine is highly lipophilic and crosses the blood-brain barrier readily.