Objective: To explore the brain levels of nitric oxide (NO) and nitric oxide synthase(NOS) in rats after sleep deprivation. Methods: NO levels and NOS activity were assayed in different brain regions of Sprague-Dawley rats after sleep deprivation by flower pot compare with normal group (CC) and tank control groups (TC). Results: NO levels and NOS activity were increased in front cortex and hippocampus after SD compared with CC and TC (P