Although many people are exposed to trauma, substantially fewer develop posttraumatic stress disorder (PTSD). Given this, studies have examined risk and protective factors for developing PTSD. This literature has established that there is a robust negative correlation between social support and PTSD. Attachment insecurity may be an informative variable to elucidating this relationship, as it is associated with both social support and PTSD. The current study used structural equation modeling to examine the relationships between attachment anxiety, attachment avoidance, general support, trauma support, and four PTSD symptom factors. It was hypothesized that (1) general support would mediate the relationship between attachment and PTSD, and that (2) trauma support would mediate the relationship between general support and PTSD. Two hundred trauma-exposed undergraduate students completed a battery of self-report questionnaires which included the Experience of Close Relationships-Revised, the Interpersonal Support Evaluation List, the Crisis Support Scale, and the PTSD Checklist. Consistent with hypotheses, social support mediated the relationship between attachment and four PTSD symptom factors, and trauma support mediated the relationship between general support and four PTSD symptom factors. These findings call attention to the particular importance of trauma support in PTSD. The results also support the need to conduct further research into the mechanisms involved in the development and maintenance of PTSD. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]