abstract the aerial parts of sideritis taurica stephan ex willd grown in egypt yielded 0.12% and 0.23% (v/w) of essential oil by hydrodistillation (hd) and simultaneous hydrodistillation-solvent (pentane) extraction (lickens-nickerson, ln), respectively. gc-fid and gc/ms analysis revealed that the two oil samples were identical in composition, but differing in the percentages of certain components. thirty-two components were identified in each, representing 92% and 93.3%, respectively. oxygenated compounds were dominant in hd oil, being 50.6% compared with ln sample (37.4%); while the hydrocarbons amounted to 41.4% and 55.9%, respectively. monoterpene hydrocarbons were mainly -pinene (11.4% and 17.7%) and -pinene (3.8% and 12.8%), respectively. the main sesquiterpene hydrocarbons were aromadendrene (4.6 % and 3.5%) and -cubebene (3% and 2.2%), respectively. the main oxygenated monoterpenes were -terpineol (2.8% and 2%) and trans-pinocarveol (1.8% and 1.4%), respectively; while the major oxygenated sesquiterpenes were -cadinol (22.4% and 12.2%), curcumenol (7.6% and 3.5%) and -bisabolol (7.4% and 2.9%), respectively. the two oil samples exhibited significant antiwormal activity against the earthworm allolobophora caliginosa, offering a support to recommendations of the possible utility of the oil of s. taurica as antiwormal agent and verifying the correlation between increased antiwormal activity of an essential oil with its high content of oxygenated compounds.