Nonmetric and metric traits were studied in cranial series representing prehistoric and modern populations of America and Siberia. Frequencies of the infraorbital pattern type II (longitudinal infraorbital suture overlaid by the zygomatic bone) are universally lower in Amerindians than in Siberians. The os japonicum posterior trace, too, is much less frequent in America than in Siberia. The only two Siberian groups with an almost Amerindian combination are late third to early second millennium BC populations from Okunev and Sopka, southern Siberia. The multivariate analysis of five nonmetric facial traits and ten facial measurements in 15 cranial series reveals two independent tendencies. One of them shows a contrast between prehistoric Siberian Caucasoids and modern Siberian Mongoloids; the second one sets Amerindians apart from others. Prehistoric people who lived west of Lake Baikal and modern Uralic speakers are intermediate between Siberian Caucasoids and Siberian Mongoloids; Eskimos, Aleuts, and Chukchi are intermediate between Siberian Mongoloids and Amerindians; and Okunev and Sopka are intermediate between Siberian Caucasoids and Amerindians. Our results suggest that people of Okunev and Sopka are collateral relatives of Amerindians with some Caucasoid admixture.