After intravenous injection of therapeutic doses of bleomycin only small amounts could be measured in glioma tissue obtained at operation in patients with malignant gliomas and the drug was rapidly cleared from the blood (T1/2 = 2 hrs). Negatively charged liposomes injected through Ommaya reservoirs into the glioma tumour bed were tolerated without observable side effect. The appearance of bleomycin in the blood and urinary clearance after intracerebral injection of bleomycin entrapped within negatively charged liposomes through an Ommaya reservoir in patients with malignant gliomas was decreased as compared with levels when free bleomycin was injected. These preliminary observations suggest a role of drugs entrapped within liposomes as a depot preparation in the treatment of human cerebral gliomas.