A laboratory study of early dating and married/cohabiting couples showed that perceived appropriateness of emotion expression was lowest for early daters' negative emotions. Partners in more developed relationships managed positive emotions less than negative emotions and less than early daters managed either negative or positive emotions. Biological sex moderated the effect of valence and relationship level on discrepancy scores, the greatest differences between stages being for males’positive emotions and females’negative emotions. A second study using partners across all stages of relationship development found evidence of a curvilinear pattern for relationship length on discrepancy scores. More management of negative emotions was reported by partners in early and later stages of relationship development. Perceived appropriateness of emotion expression was found to increase with relationship development. Females expressions of emotion were considered least appropriate in early-stage relationships. Together the results provide evidence of display rule evolution as relationships develop.