Weekly releases of Muscidifurax raptorellus Kogan and Legner and Spalangia cameroni Perkins were made for 12 wk after house cleanouts in Florida pullet houses in either spring/summer (May–August) or fall (September–December). Releases were made by weekly placement of 62,500 and 85,000 pupae parasitized by M. raptorellus and S. cameroni, respectively, which produced an average of 79,049 and 32,841 adult female parasitoids per week. House fly (Musca domestica L.) pupal mortality, as measured by sentinel pupae, was about twice as high in the release house (40.2%) as in the two control houses (21.5 and 21.8%) in the summer release. Pupal mortality in the fall was three to four times higher in the release house (45.6%) as in the two control houses (13.6 and 8.4%). Although successful parasitism of sentinel pupae was only ≈8.4% in the release houses in both studies, parasitism was significantly higher than the control houses in both summer (3.9 and 1.7%) and fall (0.0 and 0.8%) releases. Fly populations were high in both studies but significantly lower in the release houses than the controls in both summer (361.5 versus 450.3 and 584.4 spots/spot card/wk) and fall (477.1 versus 971.4 and 851.8 spots/card/wk) releases. An average of 4.8 M. raptorellus emerged from each pupa parasitized by this species, with parasite loads ranging from 1 (8.6%) to 17 (0.07%) adults emerged per parasitized pupa.