This research was based on determining the effect of risperidone in psychotic behavior induced by ketamine and its relationship with Malondialdehyde levels in brains of Rattus norvegicus var. albinus. Randomly distributed into four groups of six specimens each (White, Control Problem Problem I and II) was performed. At the White group was given intraperitoneally Physiological Saline at a dose of 10 mL / kg for 10 days and then orally for 31 days; The control group was administered intraperitoneal ketamine at a dose of 20mg / kg for 20 days and subsequently orally water ad libitum for 11 days at 20mg / kg. At Problem Problem I and II groups were administered intraperitoneal ketamine at a dose of 20mg / kg for 20 days, but on the tenth day of treatment was administered orally to parallel Risperidone 1mg / kg and 2.5mg / kg, respectively . After this process, the psychotic behavior to all g...