Specific heating of magnetic particles in radiofrequency (RF) capacitive hyperthermia and its hyperthermic effect were investigated in an in vivo study. Magnetite cationic liposomes (MCLs) were injected into a rat tumor on the femur and 8 MHz-RF capacitive heating was applied to the rat under "mild heating" conditions. Although the input power of RF capacitive heating was low under the same power conditions, the MCLs-injected tumor was heated over 43 degrees C, whereas it was only heated to 41 degrees C in the case of the rats not injected with MCLs. A necrotic area in the tumor was observed in the heated rats. From the results of histological observation of the removed tissue, the necrotic area in the MCLs-injected tumor was wider than that in MCLs-free tumor. Complete tumor suppression was observed in 71% (5 / 7) of MCLs-injected rats, and the hyperthermic effect was greatly improved by the MCLs.