Recoveries ofCoccygomimus disparis(Viereck) from pupae of gypsy moth,Lymantria dispar(L.), in Pennsylvania, Maryland, New Jersey, Massachusetts, Virginia, Vermont, New York, Nebraska, and Ontario, Canada, indicate that this Palearctic species is now well established in North America. This represents the first successful establishment of a natural enemy of gypsy moth in North America in nearly 50 yr. Levels of pupal parasitism in gypsy moth average 1.9% (maximum 13%). Historical records indicateC. dispariswas intentionally imported from India (1972), Japan (1976), and Korea (1984). Laboratory rearing resulted in the eventual release of more than 819,012 individuals liberated in 16 states. Details on the biology of this wasp, its foreign collection, introduction, release, and recovery (first in North America in 1978) are documented. Recovery fromThyridopteryx ephemeraeformis(Haworth) (Psychidae) andMalacosoma americanum(F.) (Lasiocampidae) in New Jersey andDioryctria auranticella(Grote) (Pyralidae) from Nebraska, as well as host data from outside the United States, indicates thatC. disparisis not specific to gypsy moth and should be searched for in other forest or shade tree Lepidoptera. Recent collections ofM. americanumin New Jersey showed 20.6% parasitism. Overall effectiveness as a biological control agent against the gypsy moth or other hosts remains uncertain but promising.