The Interpersonal-Psychological Theory of Suicide (IPTS) has been supported by recent research. However, the nature of the models׳ three major constructs - perceived burdensomeness, thwarted belongingness and acquired capability - requires further investigation. In this paper, we test a number of hypotheses about the predictors and correlates of the IPTS constructs. Participants aged 32-38 from an Australian population-based longitudinal cohort study (n=1167) were assessed. IPTS constructs were measured by items from the Interpersonal Needs Questionnaire (INQ) and Acquired Capability for Suicide Scale (ACSS), alongside demographic and additional measures, measured concurrently or approximately 8 years earlier. Cross-sectional analyses evaluating the IPTS supported earlier work. Mental health was significantly related to all three IPTS constructs, but depression and anxiety caseness were associated only with perceived burdensomeness. Various social support measures were differentially associated with the three constructs. Stressful events and lifetime traumas had robust independent associations with acquired capability for suicide only. The IPTS model provides a useful framework for conceptualising suicide risk. The findings highlight the importance of perceived social support in suicide risk, identify the importance of personality and other factors as new avenues of research, and provide some validation for the independence of the constructs.