Interrelationships between the three trophic levels; resistant and susceptible corn,Zea mays, a cereal aphid,Melanaphis sacchari(Zehntner), and a braconid aphid parasitoidLysiphlebus delhiensis(Subba Rao & Sharma), were studied in the laboratory and the interaction between plant resistance and the efficiency of the parasitoid was evaluated. For the assessment of parasitoid efficiency, its age-specific life tables were constructed at different host density levels. Greater survival, progeny production, female progeny and intrinsic rate of natural increase of the parasitoid were observed on the resistant cultivar than on the susceptible one. The results suggest that the reproductive success of the parasitoid was better on the corn cultivar resistant to the aphid M.sacchari, implying a synergistic effect of plant resistance on biocontrol of the aphid. Therefore, there should be no reason why plant resistance and biocontrol cannot be a highly effective and compatible combination within an IPM for aphids.