Laboratory and field experiments were conducted to determine the suitability of the oriental fruit fly,Bactrocera dorsalis(Hendel), for the development ofDiachasmimorpha tryoni(Cameron). In the laboratory, parasitism of individualB. dorsalislarvae by 6–10D. tryonieggs killed and prevented the pupation of 8.0 ± 3.7% of the parasitized hosts and the emergence of 50.0 ± 7.1% of the puparia. Mortality of immatureB. dorsalisincreased significantly as the rate of superparasitism increased. A mean of 68.0 ± 6.6% ofB. dorsalisthat received 1–5D. tryonieggs per larva pupated and eclosed to morphologically normal flies. These flies contained melanized eggs of the parasitoid in their abdomens. In uneclosed hosts which received 6–10 parasitoid eggs per larva, melanized eggs along with 1–6 melanized first-instar parasitoids were recorded. Parasitism ofB. dorsalisbyD. tryonialone never results in parasitoid development beyond the first instar. However, in a heterospecific parasitism test involvingD. tryoniandDiachasmimorpha longicaudata(Ashmead), ≈1/10 of the parasitized puparia eclosed to adultD. tryoni. Average percentage ofD. tryonifemales emerging from suchneutralized B. dorsalis(parasitized byD. longicaudatabefore or after exposure toD. tryonito block host immunity) was 81 to 92%. Emergence ofD. tryonifrom field collectedB. dorsaliswas also very low (0.35% emergence; 8D. tryoniadults out of 2,279B. dorsalispuparia). We conclude that contrary to the published host-range lists, neither laboratory-reared nor wildB. dorsalisare natural hosts for the opiine parasitoidD. tryoni.