The present work advances and tests an interdependence-based model of the associations among commitment, pro-relationship behavior, and trust. Findings from two longitudinal studies revealed good support for model predictions. Commitment-inspired acts such as accommodation and willingness to sacrifice provide diagnostic information regarding a partner's pro-relationship motives. Individuals come to trust their partners when they perceive that their partners have enacted pro-relationship behaviors, departing from their direct self-interest for the good of the relationship. The results of mediation analyses are consistent with a model of mutual cyclical growth in which (a) dependence promotes strong commitment, (b) commitment promotes pro-relationship acts, (c) pro-relationship acts are perceived by the partner, (d) the perception of pro-relationship acts enhances the partner's trust, and (e) trust increases the partner's willingness to become dependent on the relationship. Auxiliary analyses revealed that self-reported attachment style does not account for substantial variance beyond the features of interdependence that form the basis for the present model.