The extant theories in PTSD describe significant initial symptom reactions, and these reactions may provide opportunities for clearer early identification and treatment of PTSD. There are empirically identified trajectories of PTSD, which indicates there is a critical starting point to those trajectories. Generally, theories and results suggest that the re-experiencing (Cluster B) and hyperarousal (Cluster E) symptoms are common reactions after traumatic events, while hyperarousal and negative cognitions and mood (Cluster D) clusters are generally identified as the most important and/or predictive. Thus, this dissertation utilized retrospective reports in order to identify initial symptom reactions and then subsequently predict PTSD severity over time. Participants included college women who experienced sexual and relationship violence within the past 2 years. Two primary hypotheses were investigated within the dissertation: 1) Cluster B and E symptoms were expected to be the most prevalent initial reactions reported, and 2) Clusters E and D were expected to significantly predict PTSD severity over time. The results indicated partial support for each hypothesis, such that Cluster B symptoms were among the most prevalent initial reactions and Cluster D was a significant predictor of PTSD severity over time. Specifically, earlier Cluster D ordering interacted with the presence of negative beliefs and loss of positive emotions to predict PTSD severity over time.