Marilyn Strathern takes up an issue at the heart of studies of society — anthropologists using relationships to uncover relationships. The role of relations in western (Euro-American) knowledge practices, from the scientific revolution onwards, raises a question about the extent to which Euro-American kinship is the kinship of a knowledge-based society. This argument takes the reader through current issues in biotechnology, new family formations and legal interventions, as well as intellectual property debates, to matters of personhood and ownership afforded by material from Melanesia and elsewhere.