A ten-year study of the reaction and adaptability of the introduced Aoudad sheep (Ammotragus lervia) in the Palo Duro Canyon of Texas was begun in the winter of 1957-58. At that time, forty-two sheep from the McKnight Ranch, Picacho, New Mexico, were released into the halfmillion acre Palo Duro Canyon. The exotic sheep were introduced into the canyon to fill a separate ecological niche and to share the vast reaches of the canyon, noncompetitively, with native mule deer. The aoudad, a hardy big game animal, was to become a real challenge to sportsmen in the rugged terrain of the Palo Duro Canyon. The first six years of the study were spent in trying to determine an adequate census technique, habitat preference, reproduction, and sheep movement studies. In the seventh year after the aoudad sheep release, an adequate population was thought to be present in order to have a limited experimental hunt. Four, either sex, hunts have been held with 247 sheep permits being issued, and 57 aoudad sheep harvested with a hunter success of 23.08 percent. Reproductive organs, stomach, and blood samples were collected at department-operated check stations during the four hunts. Thirty-one rams and twenty-six ewes have been harvested. Of the 26 ewes, 16 were pregnant with 27 fetuses. Stomach sample analyses have indicated that shinoak, mesquite, and mountain mahogany are ,the major vegetative forms browsed by the aoudad. All blood samples registered negative to Brucellosis and three serotypes of Leptospirosis. A helicopter census initiated three years ago to determine relative sheep population has been the most successful census method to date. The helicopter is the only conveyance that can successfully cover large tracts of land in a relatively short period of time and permit observers to see firsthand where sheep range. A CO. paint pellet pistol was used experimentally Ito mark the sheep and to acquire a more reliable estimate of the population with the Lincoln Index. The aoudad sheep, since 1957, has populated and expanded their range a distance of over 20 airline miles from the two release sites. In ten years the 42 original sheep have grown into an estimated population of 600. Native to the Atlas Mountains of North Africa, aoudad sheep (Ammotragus lervia) were first imported into this country by the Jersey City Zoo on December 14, 1900. The zoo stock prospered, and other zoos and private individuals acquired the surplus aoudad sheep. In 1950, New Mexico obtained a herd of the drought-resistant sheep from the McKnight Ranch near Picacho, New Mexico, and released them near the mouth of the Canadian River gorge where native bighorn restocking programs had failed. The McKnight stock was acquired from the Hearst Ranch, San Simeon, California, which originally obtained their sheep from zoo surplus.