This article explores the potential relevance of chaos theory in understanding development and change in romantic relationships. Chaos theory implies that relationship development may not be linear, that relationships may quickly and spontaneously shift to different states and relational patterns, and that predicting their future state may be problematic. Furthermore, chaos theory generates several methodological and statistical issues for relationship studies. The application of chaos theory may increase the understanding of relation- ships as it stimulates a renewed emphasis on relationships as process, a moving from concern with predictability to emerging patterns, seeing variability as normal, and the recognition of the need for multiple perspectives and methods in studying relational development.