Nezara viridula is responsible for significant damage on cucumber, eggplant and tomato. This stink bug feeds on plant tissue causing desiccation of apices and flower bud drop; it also attacks fruits, causing deformation. Insecticides registered to control N. viridula are not compatible with natural enemies, as they disrupt integrated pest management. In a two-year trial, we evaluated the efficacy of the egg parasitoid Trissolcus basalis to control N. viridula. We tested four combinations of quantity and frequency of release of the parasitoid in the greenhouse. Each combination was repeated four times and compared to a positive control without parasitoid introduction. We observed effective control of N. viridula with the four strategies tested, but the best cost/benefit ratio was obtained with the release of 1 parasitoid/m(2)/week. The parasitism efficiency was relatively high for each strategy considered, ranging from 89 to 99%, which demonstrated a strong regulation impact on the stink bug population. Total parasitism ranged from 47 to 68%, which indicated relatively good activity and efficiency of the parasitoid, and led to a significant reduction of the damage in comparison to the control. Desiccated apices were reduced by 45 to 71% and flower bud drop by 32 to 60%. The highest damage reduction was obtained by releasing 1 parasitoid/m(2)/week. Hence, T. basalis is a good candidate for the biological control of N. viridula in protected crops. Surprisingly, the best regulation was not obtained when the highest quantity of parasitoids was released. Implications of intra-specific competition are discussed.