OBJECTIVE: Following a catastrophic natural disaster, the authors evaluated whether brief psychological intervention (debriefing 6 months later) reduced disaster-related psychological distress as measured by the Impact of Event Scale. METHOD: Two groups of subjects who had been exposed to Hurricane Iniki in Hawaii were assessed before and after participating in a multihour debriefing group. The intervention aimed to provide ventilation of feelings, normalization of responses, and education about normal psychological reactions to the disaster in a context of group support. To provide a partial control for the passage of time, the pretreatment assessment of the second group was concurrent with the posttreatment assessment of the first group. RESULTS: A repeated measures analysis of variance indicated that Impact of Event Scale scores were reduced in both groups after the treatment. CONCLUSIONS: There is preliminary empirical support for the effectiveness of postdisaster psychological intervention and for the feasibility of treatment research in postdisaster environments.