The transmission of verbal information has typically been studied within the referential communication paradigm, which has tended to use restricted tasks and simple outcome measures. In this study, new insights into the nature of communication success and failure have been obtained by the use of an approach that allows meaning to be freely negotiated. Twenty adult-child pairs were tested. Mothers were paired with their own and unrelated children in a route-giving task involving maps. All subjects played both instructor and instructee roles. The task was conducted by telephone. It was expected that related pairs would show a superior level of performance because of their history of shared experience, including language. Findings revealed a close correlation in procedures used by related compared with unrelated pairs. Number of turns taken in discourse showed that experimenter judgments of message adequacy and item selection were an overestimate of the extent of shared understanding. The role of repetition and of clarification requests in the resolution of communication difficulties is examined and compared with earlier findings from paired children of the same age as those in the study. (Author/RH)