The data on the utility of biologic response modifiers are quite sketchy. Although no true home-runs have been hit, there is evidence that some patients will benefit from these immunologic agents. The majority of studies for central nervous system tumors have been done in adults with highly aggressive anaplastic gliomas. Many of these patients had extensive disease at the time of treatment and determination of benefit is difficult. Few pediatric trials have been attempted. The evidence for efficacy for most agents is lacking, although there are encouraging responses in children with isolated leptomeningeal spread to radiolabeled monoclonal antibodies and for patients with progressive intracranial mass lesions to one form of beta-interferon. Given the limited alternatives for many of these patients, and the neurotoxicity of other means of therapy, future studies are clearly indicated in children with malignant brain tumors. The lack of evidence of efficacy in adult glioblastoma trials cannot be used as direct evidence for the nonutility of these agents for childhood brain tumors. By and large, children tend to tolerate higher doses of biologic response modifiers than adults, again raising the hope of greater utility of these drugs for pediatric patients. From the information available, it seems unlikely that these immunomodulating agents, in themselves, will be effective in the treatment of the majority of patients with brain tumors. But in combination with aggressive surgery, radiation, and possibly chemotherapy, these agents may in time add to the armamentarium available for the treatment of childhood brain tumors.