Magnetoliposomes (MLs) were conjugated with an antibody fragment to give specificity to a tumor. The antibody fragment was cross-linked to N-(6-maleimidocaproyloxy)-dipalmitoyl phosphatidylethanolamine (EMC-DPPE) in tiposomal membrane. The immobilization of the antibody fragment was optimal when the content of EMC-DPPE was 10-wt% and the reaction time for immobilization was 18 h. The Fab ' fragment-conjugating hits (FMLs) were 2.4 times higher molar immobilization density compared with the method using the whole antibody. The targetability of the FMLs to the glioma cells, U251-SP, was then investigated. The amount of FMLs uptake reached 85 pg/cell in an in vitro experiment using plastic dishes. In an in vivo experiment using glioma-harboring mice, 260 mug of the FMLs per 1 g of tumor tissue accumulated (tumor sizes was 0.1 cm(3)), which corresponded to approximately 60% of the total injection. This value was 7 times higher than that of the MLs. After injection of the FMLs, mice were exposed to intracellular hyperthermia using the alternating magnetic field irradiation. The temperature of tumor tissue increased to 43 degreesC and the growth of the tumor was found to be arrested over 2 weeks. These results indicate the FMLs could target the glioma cells ill vitro and in vivo, and are efficiently applicable to the hyperthermia of tumor.