The petroleum ether and ethanolic extract from the epigean part of Conyza canadensis exhibits a significant anti-inflammatory effect on rats with a carrageenin and formalin oedema. Eight sesquiterpenic hydrocarbons with the highest anti-inflammatory activity were found in the petroleum ether fraction (beta-santalene, beta-himachalene, cuparene, alpha-curcumene, gamma-cadinene and three other unidentified hydrocarbons). Of these substances, beta-himachalene was further studied and its anti-inflammatory activity was demonstrated.