Fourteen woodland caribou (Rangifer tarandus terraenovae) were released into a game reserve occupied by white-tailed deer (Odocoiles virginianus) with a high prevalence of the meningeal worm (Parelapostrongylus tenius). Within 6 months all of the caribou had succumbed to this parasite. The clinical, pathological, and epizootiological findings associated with this die-off are described.