<p>Seeking for new plant species as the main resources of bioactive chemicals is one of the fundamental steps in biological production science. The main objective of this paper was to screen for the allelopathic activity of Caucasian plant species in order to select the strongest allelopathic species for future studies. Dried leaves of 178 plant species collected from the Teberda State Reserve in the Caucasus region were assayed by the Sandwich method for allelopathic activity, using <em>Lactuca sativa</em> (lettuce) as the test plant. To evaluate allelopathic activity, standard deviation (SD) and SD of variance (SDV) of radicle growth inhibition were calculated. The highest (100%) inhibition was observed for <em>Artemisia austriaca</em> Jacquin, followed by <em>Oxalis acetosella</em> L., <em>Convallaria majalis</em> L. and <em>Polygonatum odoratum</em> (Miller). Among plant families, members of the Fabaceae caused greatest inhibition of radicle growth. Plants classified as “poisonous” had the highest allelopathic activities, followed closely by those designated “medicinal”. Results of this study will guide the identification of novel phytotoxic chemicals useful in medicinal and/or industrial applications.</p>