Carvacrol is the major compound of essential oils of many plants, ethnomedically used for centuries but there were no detailed investigations on its action on the cardiovascular system. The aim of our study was to investigate the role of carvacrol on the cardiovascular functions of anesthetized rats and in vitro of isolated rat aorta. Carvacrol (100 microg/kg, I. P.) decreased heart rate, mean arterial pressure and systolic and diastolic blood pressures of the anesthetized rats whereas there were no effects at 1, 10 and 20 microg/kg. Carvacrol was observed to exhibit hypotension and to inhibit N((omega))-nitro- L-arginine methyl ester ( L-NAME)-induced hypertension. The lack of inhibitory action of carvacrol (10 (-4) M) on the CaCl (2)- and phenylephrine-induced contractions of isolated rat aorta showed that neither adrenergic receptors nor voltage-dependent vascular L-type calcium channels were involved. But, based on previous investigations, the involvement of cardiac L-type calcium channel blocking actions are suggested for the hypotensive actions of carvacrol was assumed.