This prospective study assessed the temporal relationships between the symptom clusters of PTSD in two nonprobability samples of treatment-seeking victims of sexual abuse: rape victims and adult survivors of childhood sexual abuse. Both groups were assessed at three time periods using self-report measures of PTSD symptomology. Findings from two cross-lagged panel analyses indicated weak temporal relationships between the symptom clusters of PTSD; however, avoidance and emotional numbing symptoms were found to exert the strongest cross-lagged effects. Avoidance and emotional numbing symptoms were also found to be the strongest predictor of subsequently meeting caseness for PTSD in both samples. Results suggest that there are minimal cross-lagged effects between the PTSD symptom clusters after three months from traumatic exposure.