Ferrara (1994) estimates that 19-35% of the utterances by psychotherapists in session are variations of mm-hmm. However, there has been little discussion of this phenomenon in the literature. According to linguistics theory, mm-hmm constitutes a backchannel response to a speaker that affirms his or her right to continue to hold the floor. In psychotherapy, mm-hmm reaffirms the patient's right to an extended conversational turn and the therapist's role as listener. Because mm-hmm is unobtrusive and ambiguous, however, unconscious issues in the therapeutic relationship can be communicated through its variations. Psychotherapists should understand the function of mm-hmm in maintaining the structure of the therapeutic relationship and be aware that it can be easily enlisted in the service of unconscious communications.