This article is situated within the discussion started in 1962 by John Barnes, whose observations on the fluidity of social organization in the Highlands of Papua New Guinea raised the question, what binds together a certain number of individuals belonging to distinct kinship groups? Is it defense of a common territory? Is it participation in initiation rituals which institute a general order between genders and between generations? Or is it, as in the Big‐men societies, participation in cycles of ceremonial exchanges which involve all the local groups of a same region?These questions have been discussed by various authors: De Lepervanche (1967–8), A. Strathern (1968, 1970), and Feil (1981, 1984) to mention just a few.The fabric of Baruya society is generated by two principles: direct exchange of women and an elaborate system of male and female initiations. The Baruya share the same culture and the same language with their neighbours and enemies, but they distinguish and define themselves by claiming a common territory conquered at the expense of local groups and by the fact that their women circulate primarily between kinship groups residing on this territory. However, from time to time these two principles are transgressed by individuals or segments of lineages who betray their kinship or tribal solidarities, generating situations which reshape the internal composition of the Baruya tribe and its relationships with its neighbours. I intend by analysing the mechanisms of these betrayals to throw some light on this key‐moment in the dynamics of New Guinea Highlands soci