Microwave induced heating patterns in mammalian brains have been studied using spherical models through theory and experiment. Differential absorption by various portions of the brain produces local hyperthermia. Though microwave heating is extremely rapid, the precise temperature rise depends on the intensity of incident radiation and the duration of exposure. Preliminary animal experiments indicate that a temperature of 43°C is attained in 90 seconds without tissue damage, thus suggesting the possibility of using microwave differential hyperthermia as an adjunct for combination therapy for brain cancer.