✓ Thermosensitive liposomes are microscopic vesicles that can contain drugs and release them effectively in response to hyperthermia. To deliver an antitumor drug specifically to brain tumor, the authors used thermosensitive liposomes containing cis-diamminedichloroplatinum (CDDP) in conjunction with localized brain heating. The authors then investigated the antitumor effect on rat malignant glioma. Rous sarcoma virus—induced malignant glioma cells were transplanted into the brains of Fisher rats. Ten days after tumor inoculation, the rats were assigned to one of six treatment groups: control, free CDDP, hyperthermia, free CDDP + hyperthermia, liposomes containing CDDP (CDDP—liposome), and CDDP—liposome + hyperthermia. Liposomes containing CDDP or free CDDP were injected via the tail vein. Brain tumor heating was administered by means of a radiofrequency antenna designed at our institute. The rats treated with CDDP—liposome + hyperthermia had the longest survival time and the tumor CDDP level of this group was the highest when compared to the other groups. Histopathological examination showed that tumor cells were necrotized but surrounding normal brain tissue remained undamaged. On the basis of these findings we suggest that the combination of thermosensitive liposome and localized hyperthermia may better focus antitumor drugs to the tumor, providing a significantly greater antitumor effect.