Eighteen dyads (10 female and eight male), each composed so as to have one member who scored high and one who scored low on a test of personality dominance, were given a cooperative problem-solving discussion task lasting fifteen minutes. The persons with the more dominant personalities held the floor more and attempted more interruptions in proportion to their partners’ total amounts of speaking time than did those with less dominant personalities. There was also evidence that the high dominant subjects were more successful in completing their interruption attempts, although this result fell somewhat short of statistical significance. Despite the fact that the trend of the results appeared to be consistently stronger among males, there were no significant sex differences. Implications of the findings for the interpersonal communication theory of Watzlawick, Beavin, and Jackson (1967) are discussed.