Two species of European parasites,Agathis pumila(Ratzeburg) andChrysocharis laricinellae(Ratzeburg), have become established in a classical biological control project against the larch casebearer,Coleophora laricella(Hübner), in Oregon. A coarse analysis of population dynamics over 18 yr, including the periods before the population changed and as it changed, is presented for 13 plots. A detailed life table analysis over 9 yr is included for 3 of the plots. In the 10 yr before combined parasitism by introduced parasites exceeded 10%, moth density on the 13 plots averaged 52.6 per 100 buds, and parasitism was the key factor influencing population change on only 1 plot. As introduced parasites increased over the next 8 yr, however, moth density declined to 0.8 per 100 buds.A. pumilawas the key factor on all 3 plots for which a detailed life table analysis was conducted. Mortality byA. pumilaappeared to be delayed density-dependent. In the most advanced plots, mortality of larvae caused byA. pumilaseems to be stabilizing moth numbers at low density. Final evaluation, however, awaits further long-term measurements.