Oral tranquilizers were mixed with a grain bait and fed to pronghorn (Antilocapra americana) in an attempt to immobilize and thus facilitate their capture. Diazepam, administered at 6 mg/kg body weight immobilized a tame pronghorn fawn within 30 min. Tranquilization was still apparent after 8 h. A minimum dose of 23 mg/kg body weight was necessary to immobilize a wild adult pronghorn. Immobilization occurred after 60 min and tranquilization was apparent 24 h post ingestion. Excitement severely impeded the effect of the drug and although easily captured, the animal struggled wildly when handled. Wild pronghorn fawns showed moderate tranquilization when administered diazepam at 23 mg/kg body weight but were unapproachable. Doses of diazepam between 13 and 23 mg/kg body weight were used to capture tame yearling and adult pronghorn held in a 132 ha enclosure. A dose of 23 mg/kg body weight was excessive in that the animals did not recover for 48 to 54 h post ingestion and had difficulty maintaining a sternal bedding position. Diazepam at 13 mg/kg body weight failed to tranquilize the animals sufficiently for easy capture. Promazine hydrochloride at doses of 2 to 17 mg/kg body weight, given orally to wild pronghorn fawns and an adult, did not produce visible signs of tranquilization. Animals refused to eat bait containing doses of promazine hydrochloride greater than 17 mg/kg body weight.