The effect of Pistacia lentiscus L. leaf extracts (aqueous, 30%ethanol and 70% ethanol) was studied on the rat isolated trachea. Pistacia lentiscus L. extracts induced a relaxation on basal tone and precontracted trachea. On the rat isolated trachea precontracted by acetylcholine 10-3M, Pistacia lenticus L. leaf extracts (aqueous, 30% ethanol and 70% ethanol) induced a relaxation. EC50 values for the 70% ethanol, 30% ethanol and aqueous extractswere respectively: 1.00.10-3 ± 0.11, (n = 15), 1.71.10-3 ± 0.09 (n = 8) and 1.75.10-3 ± 0.12 g/ml (n = 12). The relaxation to Pistacia lentiscusL. 70% ethanol extract was 182.14 ± 17.52%(n = 15) of the response to theophylline 3.10-3M.Atropine, propranolol, phentolamine (10-7M) and indomethacin (10-6M) did notmodifyPistacia lentiscus L. induced relaxation. Forskolin (10-6M) andmethylene blue (3.10-5M) respectively potentiated and antagonized Pistacia lentiscus L. relaxation. The studied extract (10-6 to 10-4 g/ml) did not affect theophylline, IBMX (3-isobutyl-1-methylxantine, nifedipine, dipyridamole, rolipramand siguazodamconcentration-response curves but caused in a dose dependent manner left shift to those of captopril, sodium nitroprussiate, 8 phenyltheophylline and enprofylline. Moreover, the extract induced total reversal of the zaprinast-induced relaxation. On precontracted rat trachea, adenosine induced contractile response and predominant relaxation. Pistacia lentiscus L. blocked adenosine contractile response and potentiated the purine nucleosie relaxation. It is suggested that the recorded relaxation induced by the studied drug involves several mechanisms of action including an inhibition of angiotensin I converting enzyme (ACE), an interaction with phosphodiesterase (PDE) V and an interaction at adenosine receptors level.