Military service members and veterans now show high rates of suicidal behavior, relative to civilians. Research has highlighted several risk factos that may serve as triggers for episodes of acute suicidality, with one of the strongest and most supported predictors of suicidal behavior being interpersonal problems. Unfortunately, little research has assessed the mechanisms by which interpersonal risk factors for suicide may become exacerbated. The proposed investigation addresses the NIMH mission to determine modifiers of maturational and illness trajectories, emphasizing periods of sensitivity to perturbation and/or potential for intervention by collecting daily dyadic data on a range of adaptive and maladaptive interpersonal processes, together with the primary suicide risk factors of perceived burdensomeness (PB), thwarted belongingness (TB), and perceived unlovability (PU), and suicidal ideation (SI). By analyzing the day-to-day associations among interpersonal variables and suicide risk factors and ideation, the study will illuminate interpersonal processes that may heighten or protect against acute exacerbations of suicide risk that may lead to suicidal behavior. The long- term objective of this research is to generate potential targets for interventions that aim to reduce risk of suicidal behavior in service members and veterans. The first aim of the study is to evaluate concurrent and prospective associations of maladaptive interpersonal processes (e.g., marital conflict, communication patterns) with PB, TB, and PU, and subsequent suicidal ideation and intention. The second aim is to evaluate concurrent and prospective associations of adaptive interpersonal processes and behaviors with these same risk factors and SI, to attempt to identify potential protective factors. The third aim is to evalute how other established risk factors (hopelessness and perceived unbearability of problems) may moderate the hypothesized associations among the proposed interpersonal mechanisms and suicide risk factors. Data will be gathered daily for 14 days to evaluate associations over time. This approach will allow for use of multiple time points, to maximize the chance of detecting meaningful fluctuations in suicide risk. Findings will increase scientific knowledge about potentially malleable interpersonal risk and protective factors of suicidal behavior, thus enabling clinical scientists to refine existing interventions and or/design novel interventions to prevent suicidal behavior in service members and veterans. The goals of the proposed study will be accomplished within the context of a research training program aimed at developing expertise in pathological stress reactions and interpersonal processes, military populations, longitudinal, dyadic methodology and data analysis, grant writing, and dissemination of research. The training plan includes completion of relevant courses, attendance at targeted workshops, scientific writing and presentation experience, and individual supervision and mentorship by a Sponsor and co-Sponsor who have complementary areas of expertise.