Factor analytic studies of trauma victims' posttraumatic stress disorder (PTSD) have offered conflicting hypotheses about how to conceptualize PTSD into symptom categories. The present study used confirmatory factor analyses of self-reported PTSD symptomatology from 5,664 child and adolescent victims of Hurricane Hugo to compare 10 models of PTSD dimensionality. PTSD was best represented by a 2nd-order PTSD factor that manifests in 3 symptom clusters (Intrusion/Active Avoidance, Numbing/Passive Avoidance, and Arousal). This model was cross-validated on 3 age groups (late childhood, early adolescence, and late adolescence), and results indicated factorial invariance across groups. PTSD symptoms varied in relative centrality to the underlying dimensions of PTSD, which differed in their relations with anxiety and degree of traumatic exposure. Implications for classification criteria and an empirically supported theory of PTSD are discussed.