Data and observations on the use of Etorphine hydrochloride (M99) (in combination with Acepromazine) and its antagonist M50-50 for immobilization of captive elk (Cervus elaphus canadensis) are presented. The study period covers 3 years during which 8 adult elk were immobilized 52 times with M99. The average dose of M99 administered for each immobilization was 2.2 mg per 100 kg body weight. Reversal with M50-50 was effected by an average dose of 4.4 mg per 100 kg body weight. Induction averaged 5.9 minutes while reversal took an average of 4.6 minutes.