<p class="042abstractstekst">In the present study the bioherbicidal activity of essential oils hydrodistilled from <em>Nepeta glocephalata </em>Rech.f and <em>N</em>. <em>ispahanica</em> Boiss were investigated on four weed species (barnyard grass (<em>Echinochloa crus-galli</em> (L.) Beauv), redroot pigweed (<em>Amaranthus retroflexus </em>L.), lambsquarters (<em>Chenopodium album </em>L.) and canary grass (<em>Phalaris canariensis </em>L.)). A total of 37 components were identified from the essential oils of <em>N. glocephalata and N. ispahanica</em> constituting approximately 98.61 % and 96.1 % of the oils, respectively. In laboratory bioassay different concentrations (0, 1, 2, 4 and 8 μl ml^-1) of two <em>Nepeta </em>essential oils on germination, root and shoot length were studied. Results showed by increasing the concentration of oils, all studied traits of the weeds were decreased compared with control. In a glass house bioassay post-emergence application of <em>Nepeta</em> essential oils (1.25 %, 2.5 %, 5 % and 10 %, v/v) on 3-week-old weed plants caused visible injury (7-days after spray) ranging from chlorosis to necrosis of plant weeds. In foliar application under glasshouse conditions, both<em> Nepeta</em> essential oils reduced the seedling dry mass and concentrations of chlorophyll a chlorophyll b. The study concludes that <em>Nepeta</em> essential oils have phytotoxic effects and could be used as bioherbicides but the selectivity of these compounds should be considered also.</p>