The present article illustrates the experimental results of acute and sub-acute toxicity of crown-ethers (12-crown-4, 15-crown-5, and 18-crown-6). The experiments were performed upon biological objects of different complexity of structure-functional organization. Crown-ethers impaired growth and reproduction of Daphnia and unicellular Algae at 5 and 10 mg/l concentrations and caused toxic action upon tissue cellular culture (J929, X-63, Hep-2, Vero) and buccal epithelium at 0.05 and 0.5 mg/l concentrations. Cytotoxic action of the investigated xenobiotics was connected with DNA, RNA, and protein biosynthesis disturbances. The results of experiments with rats, mice, and guinea-pigs showed crown-ethers to be moderately toxic and extremely cumulative substances. The cellular cultures and buccal epithelium could be used in express-evaluation of biological activity of newly synthesized xenobiotics, as the reliable indexes of determination of potential danger of chemical compounds for warm-blooded animals.