Acetone extract of Sideritis trojana and ent-kaurene diterpenoids 7-epicandicandiol, and 18-acetylsideroxol showed toxicity against Acanthoscelides obtectus and Sitophilus granarius while 7-epicandicandiol diacetate showed toxicity against Ephestia kuehniella. The P-values' tests were carried in order to show statistical significance of dose and time against insects. Insecticidal activity increased with amount of doses for A. obtectus, however it did not increase with time. The similar results were observed for Sitophilus granarius while the mortality percentages of E. kuehniella increased with both amount of doses and time, however, after 96th hour, toxicity of compounds almost did not change oil the latter insect. (c) 2005 Elsevier B.V. All rights reserved.