Pupae and adults ofApanteles melanoscelus(Ratzeburg) (Hymenoptera: Braconidae) were released in 5 plots in 3 sites in Connecticut during the summers of 1973 and 1974. Gypsy moth numbers varied from low to high in the different sites. Weekly collections of caterpillars showed consistently greater percent parasitism byA. melanoscelusin the release plots than in the check plots at all 3 sites for at least the first 2–3 wk after release. In later collections no differences occurred in the 2 sites where gypsy moth numbers were low. In the site with high host numbers, percentage parasitism in the release plots were higher than in the checks even at the 7th weekly collection after release.