Combat veterans are at an increased risk for the development of full and subclinical PTSD. Although research has shown that social support from romantic partners is implicated in the remittance of PTSD symptoms, service members with PTSD are also at increased risk of marital discord and divorce. This negative cycle of risk between PTSD symptoms and marital discord has been studied broadly, but less attention has been paid to the daily interactions between service members and their partners that may exacerbate the cycle. The proposed investigation addresses the NIMH mission to use novel scientific perspectives to promote prevention, recovery, and cure in mental illness by using experience sampling methods to collect self-report data on symptoms and behaviors from service members with clinical or subclinical PTSD and their romantic partners over 14 consecutive days. By analyzing the day-to-day associations among symptoms and interpersonal behaviors, the study will illuminate specific interactions between partners and service members that are most likely to reduce or increase PTSD symptoms over time. The long-term objective of this research is to generate potential targets for interventions that aim to reduce relationship distress in military couples with PTSD. To that end, the specific aims of the study are threefold. First, the study will evaluate the impact of individual symptoms of PTSD in service members on subsequent interpersonal emotions and behaviors in service members and their spouses, to help clarify which symptoms are particularly related to specific types of interpersonal problems in military couples. Second, the study will evaluate the impact of spouses' feelings of intimacy and distress on their subsequent provision of support to service members, to clarify whether partners' intimacy and distress impact their actual behavior toward those with PTSD symptoms. Third, the study will evaluate the relationship of spouses' support provision to subsequent PTSD symptoms in service members, to determine the actual effect of partner behaviors on service members' PTSD symptoms. Data collected in the proposed study will substantially increase scientific knowledge about the interpersonal relationships of those with combat-related PTSD, and enable clinical scientists to refine existing couple's interventions and/or design novel interventions for PTSD. The scientific perspective afforded by the design and the clinical utility of results both have the potential to contribute substantially to prevention and treatment of PTSD in a growing number of military service members. The goals of the proposed study will be accomplished within a research training program aimed at developing expertise in PTSD, experience-sampling methodology and data analysis, dyadic relationships, and the military context. The training plan includes completion of relevant courses, attendance at targeted workshops, individual supervision and mentorship by experts in the field, and scientific writing and presentation experience.