This paper examines the role of retracted tongue root ([RTR]) harmony in Northeast Asian areal and genetic relationships. Recent research has suggested that at least three of the families grouped together as Altaic by Poppe (1960)-Korean, Mongolic, and Tungusic (KMT) -should be reconstructed with [RTRI vowel harmony. ln this paper we reinforce this conclusion, arguing specifically against proposals that [RTRI hannony is secondary, or that [ATR) is the dominant feature. We also argue against the proposal of Starostin et al. (2003) that specific proto-families such as proto-Tungusic should be reconstructed without vowel harmony. We then compare the status of [RTR) hannony in Northeast Asia to the status of tongue root harmony in the Centrai.Sudanic Zone, extending our discussion to the vowel harmony found in Chukchi, Yukaghir, Nivkh, and Ainu. We discuss whether KMT-style [RTR) harmony should be viewed as an innovation or a retention, and examine the particular issue of the Korean vowel inventory.