Malignant astrocytoma is a fatal, primary brain tumor affecting adults in the prime of life. Even with optimal treatment, median life expectancy from time of diagnosis is 51 weeks. Standard therapy consists of surgical debulking, radiation therapy and chemotherapy. Immunotherapy, utilizing biologic response modifiers (BRMs), affords one of the more promising treatment modalities. ImuVert, a BRM derived from Serratia marcescens, was recently granted orphan drug status by the Food and Drug Administration. In phase I and II clinical trials in patients with advanced malignant tumors, toxicities ranged from mild local reaction at injection sites to hypotension requiring vasopressors. ImuVert is currently being tested in a multicenter clinical trial as a treatment for recurrent malignant astrocytoma in adult patients. A comprehensive toxicity profile of brain tumor patients receiving ImuVert and techniques of managing adverse effects is presented.