The volatile compounds produced by the leaves of Trifolium glanduliferum, T. strictum and T. subterraneum were collected by trapping on Tenax TA adsorbent and the major components were identi®ed by GC±MS. The volatiles obtained from T. glanduliferum and T. strictum were shown to deter the redlegged earth mite (Halotydeus destructor) from feeding, whereas those from T. subterraneum did not. b-Ionone and coumarin, detected in the volatiles of T. glanduliferum, T. strictum, showed strong deterrent activity at 100 ppm. Phenylethanol, a component of the volatiles of T. strictum, was inactive.