The thesis advanced in this essay is that couple relationship interventions are central to effective therapy with many adult clients. I begin by reviewing a body of evidence that demonstrates the significance of couple relationships in the lives of most adults. A range of circumstances are described in which effective therapy with adults needs to address the couple relationship, even when the couple relationship is not mentioned as a presenting issue. It is concluded that individual psychological adjustment often is best understood when conceptualised within the intimate interpersonal context of the couple relationship.