<jats:title>Abstract</jats:title><jats:p>The essential oils of <jats:italic>Mentha rotundifolia</jats:italic> and <jats:italic>Mentha longifolia</jats:italic> were analyzed with GC and GC/MS. The major components were rotundifolone (10.4%) and piperitol (57.6%) in <jats:italic>M. rotundifolia</jats:italic>, and rotundifolone (33.2%) and diosphenol (47.7%) in <jats:italic>M. longifolia. M. longifolia</jats:italic> essential oil exhibited a stronger CNS depressant effect than that of <jats:italic>M. rotundifolia</jats:italic>; both essential oils were somnifacients.