The antihelminthic effect was determined in Enchytraeus sp. No 80 strain (20 helminths in 2 ml of 0.5% NaCl solution and 0.01 phosphate buffer at 7.4, room temperature, evaluation after 24 hours) and Ascaris lumbricoides suis (5 females in 200 ml of Ringer's solution in the case of thermolability, at 37°C, after 24 hours) and by kymography on the izolated preparation of Ascaris lumbricoides suis (Ringer's solution, 37°C, reaction within 10 minutes, calculated in relation to standard reaction taken as 100). DL₅₀ was calculated by own method (Wiad. Parazytol., 1961). It has been found that the strongest action on Enchytraeus is exerted by glycol methylene ether (DL₅₀ = 0.19±0.21 m) and piperazine adipinate (0.15 ± 0.63 m); twice weaker is the action of glycol ethylene ether, eight times weaker that of thylene and propylene glycols. In Ascaris lumbricoides the strongest antihelminthic action was exhibited by ethylene glycol ethyl ether (0.47 ± 0.01 m), twice weaker by methylene ether, 3-4 times weaker by ethylene and propylene glycols. Propylene glycol and methylene ether depressed the tonus of A lumbricoides preparation by 50% within 10 minutes at concentrations approaching lethal ones, whereas the remaining glycols acted twice weaker. Piperazine adipinate had neither killing action on the parasite nor depressing effect on the tonus of the preparation. The relative toxicity index (DL₅₀ for mouse: DL₅₀ for helminth) is the most favourable for propylene glycol (130), then for ethylene glycol (65), ethylene glycol ethyl (52) and methyl ether (30).