This chapter provides caution about the broadly based and extensive use of debriefing in communities affected by disasters. Psychological debriefing is an intervention intended to facilitate the prevention of, or recovery from, the adverse psychological sequelae of traumatic events. The data collected in the investigation of the psychosocial sequelae of the 1989 Newcastle earthquake provided an opportunity to examine the effectiveness of psychological debriefing. The naturalistic study design used in the investigation, together with an approach to data analysis that controlled for potential confounds, supports the validity of the results, which, in turn, concur with those of other naturalistic studies of debriefing as well as those employing a randomized controlled design. Debriefing identifies the lack of awareness of post-trauma stress responses as a target for change for which information is the putative change agent. It may also be that debriefing is helpful in unintended ways less accessible through measurements.