Eurytoma tephritidis Fullaway (Hymenoptera: Eurytomidae) is an exotic solitary larval endoparasitoid that has been recorded to parasitize gall-forming tephritids in Hawaii. We surveyed E. tephritidis parasitism of Tetreuaresta obscuriventris (Loew.), Ensina sonchi (L.), Acinia picturata (Snow), Procecidochares utilis Stone, P. alani Steyskal, Trupanea sp. nr. cratericola, and T. dubautiae (Bryan) (Diptera: Tephritidae) on four major Hawaiian islands. No wasps emerged from T. obscuriventris and E. sonchi. Among other species, percent parasitism ranged from less than 1% to over 67%, depending on fly species and sampling location. Overall, E. tephritidis showed higher affinity for gall-forming tephritids than flowerhead-feeders, although it parasitized substantial numbers of the native flower-infesting T. sp. nr. cratericola. The implications of our findings for a more accurate estimation of the risks posed by biological control programs to non-target fruit flies in Hawaii are discussed. [Full Text]