Abstract: The composition of the essential oil from the fruit seeds of Monodora myristica Gaertn. (Annonaceae) was studied by capillary gas chromatography. The analysis using a combination of retention indices and combined Gas Chromatography/Mass Spectrometry (GC/MS) led to the identification of 30 components. The oil contains mainly monoterpenoids (93.2%) out of which 77.4% are monoterpene hydrocarbons and some sesquiterpenoids (5.8%) The major constituents were α-phellandrene (34.4%) and p-cymene (22.2%). The essential oil effects on the cardiovascular system were studied by recording the amplitude and frequency of the frog isolated heart contractions and by recording arterial blood pressure variations of the guinea pig. At the dose of 40, 80 and 120 μL kg-1 the essential oil induced a hypotensive effect on the blood pressure and at the dose of 0.01-0.05%. It reduced significantly the cardiac contractions of the isolated heart; however at 0.06% it totally stopped the cardiac contractions. Both these effects conducted in the present study could contribute to the anti hypertensive activity of the Monodora myristica essential oil.