The effect of a methanol extract, obtained from the roots of Ocimum sanctum, on mouse swimming performance were studied using three different doses. On the basis of our findings, a high dose (400 mg/kg, i.p.) of the extracts of Ocimum sanctum increased the swimming time suggesting a central nervous system stimulant and/or antistress activity. The effect produced by the extract was comparable to that of desipramine, an antidepressant drug. Copyright © 2000 John Wiley & Sons, Ltd.