One key task of research in relational communication is to understand how relational knowledge guides communicative processes. A necessary step in that direction is to determine what form of relational knowledge guides the cognitive processes involved in producing and comprehending messages. Based on tests of other forms of social knowledge, the best unobtrusive indicator of relational knowledge was determined to be systematic distortions in memory. Three forms of relational knowledge—general dimensional knowledge, situation-specific knowledge, and behavior-specific knowledge—were contrasted for their ability to account for biases in memory for relational implications of remarks in conversations. Two sets of results were noteworthy. First, very strong effects on both accuracy and direction of memory were found, indicating that some form of relational knowledge guided memory for conversations. Second, when the three forms of relational knowledge were contrasted, only one—behavior-specific knowledge—accounted for a significant proportion of those memory effects (83% for accuracy and 85% for errors). The findings challenge the validity of well-established dimension- and situation-based approaches to relational knowledge and suggest alternative approaches that may be more compatible with the uses to which relational knowledge is put in communication.