We develop and test a theory of relational cohesion, which predicts how and when people in exchange become committed to their relationship. The theory focuses on dyads within networks and predicts that more equal power and greater total, or mutual, power promote exchanges that arouse positive emotions and create perceptions of the relation as a cohesive unit. The behavioral consequences are a tendency for actors to (1) stay in the exchange relation despite attractive alternatives, (2) provide each other token gifts, and (3) contribute to a new joint venture. Three laboratory experiments test and support the theory. Our results suggest that complementary emotional/ affective and uncertainty-reduction processes explain the effect of repetitive exchanges on commitment formation. The broad implication is that frequent exchanges by the same actors in a network result in their relation becoming a valued object in itself and a source of informal constraint on malfeasance.