This study examined posttraumatic stress disorder (PTSD) and comorbid disorders in 70 preschool children (ages 3-6) and their caregivers following Hurricane Katrina. Children's rate of PTSD was 50.0% using age-modified criteria. The rate of PTSD was 62.5% for those who stayed in the city and 43.5% in those who evacuated. Of those with PTSD, 88.6% had at least one comorbid disorder, with oppositional defiant disorder and separation anxiety disorder being most common. Caregivers' rate of PTSD was 35.6%, of which 47.6% was new post-Katrina. No children and only 2 caregivers developed new non-PTSD disorders in the absence of new PTSD symptoms. Differences by race and gender were largely nonsignificant. Children's new PTSD symptoms correlated more strongly to caregivers with new symptoms compared to caregivers with old or no symptoms. (Contains 4 tables.)