In Oregon, winter moth,Operophtera brumata(L.), is distributed throughout the northern region of the Willamette Valley, where it is commonly found on commercial hazelnut,Corylus avellanaL.; crabapple,Malus silvestrisMill.; and flowering plum,Prunus cerasiferaJ. F. Ehrh. Adults emerge in early November through December, eggs overwinter, larvae eclose in mid-March and develop through five instars, and pupae occur in the soil from May to November. Six species of native parasitoids were reared from field-collected larvae, but parasitism averaged only 4.5 and 12.2% in 1980 and 1981, respectively. The exotic parasitoidsCyzenis albicans(Fallén) (Tachinidae) andAgrypon flaveolatum(Gravenhorst) (Ichneumonidae) were released for biological control of winter moth in 1981 and 1982.C. albicanswas recovered from four of seven release sites. NoA. flaveolatumhave been recovered