AlthoughTelenomus alsophilaeViereck is important in the natural control of a hardwood defoliator,Alsophila pometaria(Harris), its parasitization capabilities and host range are largely unknown. Initially, eggs of a laboratory host,Abbotana clemataria(J. E. Smith), were exposed to mated females each day from deposition till eclosion. Although eggs during all stages of development were attacked, only unembryonated eggs were parasitized successfully. Infertile eggs of the same host also were parasitized but less effectively than comparable numbers of fertile eggs. Among 22 prospective hosts in 5 families of Lepidoptera,T. alsophilaeparasitized 12 species of geometrids and 2 of noctuids. It was concluded that the broad host potential for this parasite offers some new opportunities for biological control work against forest pests that previously were not anticipated.