This contribution focuses on the language situation in two different communities of the Middle Sepik area, speaking closely related languages of the Ndu family ? the Manambu and the Yalaku. The two groups maintain traditional features typical of "river-dwellers" who live on the banks of the Sepik River (the Manambu) and those who live of the River, or "jungle-dwellers" (the Yalaku), including subsistence and exchange patterns. Due to a history of interactions with the Kwoma-speaking people, the Yalaku language has incorporated numerous borrowings and grammatical calques from Kwoma (not genetically related to the Ndu family to which both Manambu and Yalaku belong). In contrast, there is hardly any Manambu-Kwoma multilingualism. A major difference between the two groups lies in the high number of loans from Tok Pisin in Manambu and the scarcity of them in Yalaku. The paper addresses the changes in the lifestyles of the two groups, contrasting their responses to social and cultural changes as reflected in linguistic change and in attitudes to language.