The objects of the study were Ephedra procera Fisch (Fam. Ephedraceae), Taxus baccata L. (Fam. Taxaceae) and Mahonia aquifolium (Pursh) Nutt (Fam. Berberidaceae) growing or introduced in Georgia.Biologically active alkaloid-containing substances were obtained by liquid-liquid extraction. In all studied species, the dominant alkaloids belong to the acyclic, diterpene and isoquinoline groups of alkaloids, respectively.In vitro cytotoxic activity was evaluated on A-549 (lung carcinoma cell lines), DLD-1 (colon adenocarcinoma cells) and WS-1 (human fibroblast normal cell lines). The sums of alkaloids obtained from Ephedra Procera showed selective cytotoxic activity against A-549 and DLD-1. An alkaloid enriched fraction isolated from Taxus baccata L. demonstrated significant specific cytotoxic activity against A-549 and DLD-1 cell lines. The sums obtained from Mahonia aquifolium exhibited pronounced activity against all cell lines -A-549, DLD-1 and WS-1 according to the Resazurine and Hoechst models.