Knowledge as to how attachment behavior is observable in couple interaction can be very useful to clinicians who use attachment theory or related theories to guide their work with couples. The development of the Adult Attachment Behavior Q-Set (AABQ), a 100-item Q-sort designed to be consistent with Main's Adult Attachment Interview (AAI) coding system, is described. Videotaped discussions were coded for a sample of 28 couples. The majority of the couples were married and had sought therapy for couple problems. Reliability of coding was adequate. Evidence for validity was promising, with a match of 84% between the AAI and AABQ for secure versus insecure, and 70% for the three categories of secure, dismissing, and preoccupied. Even though additional reliability and validity information are needed for the AABQ, it holds promise for providing insights into couple dynamics that could be useful in guiding interventions and in evaluating the outcome of couple therapy.