Effects of novobiocin, nalidixic and oxolinic acids, which are potent antibacterial agents, on the survival and development of the hymenopterous endoparasitoid, Pimpla turionellae L. (Ichneumonidae) were investigated alone by rearing the larvae aseptically on chemically defined synthetic diets. Survival of the fifth instar larvae was not significantly affected by diets with different levels of antibiotics tested. A diet containing the lowest level of novobiocin significantly increased yields of pupae and adults. This level also significantly shortened the developmental time for fifth instar but had no significant effect on complete development of the larvae up to adult emergence. Oxolinic acid at the lowest level did not affect the survival but prolonged development of the insect. In general, the rate of development was significantly increased and the survival was decreased with high levels of the antibiotics. However, nalidixic acid caused a striking decrease in the survival at all tested levels. These results suggest that novobiocin and to a lesser extent oxolinic acid are compatible for addition to artificial diet for rearing P. turionellae, which is an important parasitoid used in biological control. none