Therapeutic hypothermia can improve neurological recovery and reduce mortality in acute stroke. Pharmacologically-induced hypothermia (PIH) has been investigated in preclinical and clinical studies. Usually the core temperature (rectal or esophageal) is measured to monitor the temperature changes of the subject during the treatment. However, it remains unknown how the brain temperature is affected by PIH as the brain temperature can be different from the core temperature and affected by the anesthesia. In the present study, the brain temperature changes of adult rhesus monkeys maintained under isoflurane for over 3 hours were examined and evaluated using diffusion MRI.