Previous research on natural disasters has been limited by a lack of predisaster data and statistical analyses that do not adequately predict change in psychological symptoms. In the current study, we addressed these limitations through analysis of 3 waves of data from a longitudinal investigation of 313 low-income, African American mothers who were exposed to Hurricane Katrina. Although postdisaster cross-sectional estimates of the impact of traumatic stress exposure and postdisaster social support on postdisaster psychological distress were somewhat inflated, the general trends persisted when controlling for predisaster data (B = 0.88 and −0.33, vs. B = 0.81 and −0.27, respectively). Hierarchical linear modeling of the 3 waves of data revealed that lower predisaster social support was associated with higher psychological distress at the time of the disaster (β = −.16), and that higher traumatic stress exposure was associated with greater increases in psychological distress after the storm (β = .86). Based on the results, we suggest that the impact of traumatic stress on psychological trajectories cannot be accounted for solely by preexisting risk, and recommend more complex research designs to further illuminate the complex, dynamic relationships between psychological distress, traumatic stress exposure, and social support.