Crude ethanolic extract of the stem bark of Terminalia arjuna (Combretaceae) and its three compounds namely arjunic acid, arjungenin and arjunetin were evaluated for antifeedant, growth inhibitory and oviposition-deterrent activities against a lepidopterous insect Spilarctia obliqua. The compound arjunetin showed highest growth inhibitory and feeding-deterrent properties with a growth inhibition (GI(50)) and feeding-inhibition (FD(50)) of 188.5 and 287.1 micro g/g diet respectively. Oviposition bioassays indicated no oviposition-deterrence in any of the compounds tested. The structure-activity relationship study indicated the importance of a glycosidation linkage in arjunetin.Copyright 2004 John Wiley & Sons, Ltd.