Although communication and uncertainty reduction are almost thought to go hand-in-hand, it is possible for communication to increase uncertainty if new information is inconsistent with prior knowledge and undermines it. As an initial step toward understanding the neglected side of uncertainty, reports were gathered on types of events that increase uncertainty in interpersonal relationships, their emotional and cognitive impact, the uses of communication in dealing with them, and their effects on the relationship. Results indicated that almost everyone could remember experiencing such an event, that there were six major types, and that the impact on emotions, beliefs about the other person and the relationship were very strong. The majority of relationships were terminated or became less close as a result of the event but many were unaffected or became closer, depending on communicative, cognitive, and emotional variables. The findings have important implications for studying communication in relational dissolution and the accommodation of social knowledge to inconsistent information.