Caves in the western foothills of the Altai Mountains have long been known, and collections of Pleistocene fauna were made a century ago in caves in the middle reaches of the Charysh River which rises in the snow-covered Kargon range on the central Altai. The cave near the village of Ust'-Kan in the upper reaches of the Charysh River, which was discovered and excavated in 1954, is the first Siberian cave site of Paleolithic age to be investigated. The deposits contained a rich and varied fauna including 17 species of mammals and 12 of birds. Of special interest are the extinct spiral-horned antelope and cave hyena. This is the first Paleolithic site at which the yak has been found. This faunal assemblage is typical of a steppe region such as the dry, unforested Central Asiatic tablelands, and is quite distinct from the postglacial fauna from the known open sites of the Siberian Paleolithic in the Yenisei, Angara, and Trans-Baikal regions. The occupation of the site is dated by the fauna to the warm phase just preceding the last Altai glaciation. The artifacts exhibit the massive and archaic characteristics typical of the Siberian Paleolithic in general, but differ completely from artifacts at previously known Late Paleolithic sites considered to be contemporaneous with the European Magdalenian and later. The Ust'-Kanskaia tool assemblage is in the Mousterian tradition and may be related to the Levalloiso-Mousterian developments in neighboring Central Asia. Comparative artifact and faunal studies also suggest correlations with the Upper Paleolithic of the Ordos and the ancient cultures of Southeast Asia.