A battery of neuropharmacological experiments showed the hot water extract of Ocimum sanctum Linn. (Labiateae) had a depressant effect on the central nervous system (CNS), but the aqueous extract showed no effect on it. The hot water extract reduced the spontaneous locomotor activity, exploratory head dipping, propulsive locomotion and exploratory ambulation as well as prolonged the pentobarbital induced sleeping time. The depressant effect starts from 60 minutes after the drug administration and continued to 180 minutes. The drug may exert central depressant effect by interfering with the function of the cortex.