This is a study of the relation between the Greater Awyu (Awyu-Dumut, Ndeiram, and Becking-Dawi) and the Greater Ok (Ok and Oksapmin) languages, both considered part of the Trans-New Guinea (TNG) group of languages. The first part of this paper considers an earlier proposal by Voorhoeve, who argues that the Awyu-Dumut languages and the Ok languages form a (genealogical) subgroup within TNG, basing his conclusion on a combination of lexical evidence and a single piece of evidence from shared bound morphology. We review the lexical evidence, and then look for additional cases of bound morphology shared between the two groups. As we do not find any cases of shared bound morphology that convincingly support a genealogical subgrouping, we conclude that the similarities between the Greater Awyu and Greater Ok languages are more likely to be the result of contact, rather than of genealogical ties below the level of TNG. The second part of this study discusses the question of whether contact was old or more recent, and focuses on contact between the two neighboring languages Muyu (Ok) and Mandobo (Awyu-Dumut). Speakers of the two languages share many cultural traits, and contacts between the two groups, through trade and intermarriage, are rather intensive. We show that, despite contact, linguistic similarities are surprisingly few, and we suggest some explanations for this. © by University of Hawai'i Press. All rights reserved.