Exchange events are fundamental building blocks of business relationships and essential to relationship development. However, some events contribute to incremental relationship development, as predicted by lifecycle theories, whereas others spark "turning points" with dramatic impacts on the relationship. Such transformational relationship events (TREs) are encounters between exchange partners that significantly disconfirm relational expectations (positively or negatively), result in dramatic, discontinuous change to the relationship's trajectory, and often reformulate the relationship itself. With a three-study, multimethod design, the authors (1) establish a foundation for differentiating dramatic and incremental exchange events on the basis of relational versus product expectations and disconfirmations, thus revealing that strong relationships benefit product but harm relational disconfirmations; and (2) conceptualize, define, and differentiate TREs from other types of disconfirming events, then link them to exchange performance.