Objective: To estimate the prevalence of serious emotional disturbance (SED) among children and adolescents exposed to Hurricane Katrina along with the associations of SED with hurricane-related stressors, sociodemographics, and family factors 18 to 27 months after the hurricane. Method: A probability sample of prehurricane residents of areas affected by Hurricane Katrina was administered a telephone survey. Respondents provided information on up to two of their children (n Euro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin) 797) aged 4 to 17 years. The survey assessed hurricane-related stressors and lifetime history of psychopathology in respondents, screened for 12-month SED in respondents' children using the Strengths and Difficulties Questionnaire, and determined whether children's emotional and behavioral problems were attributable to Hurricane Katrina. Results: The estimated prevalence of SED was 14.9%, and 9.3% of the youths were estimated to have SED that is directly attributable to Hurricane Katrina. Stress exposure was associated strongly with SED, and 20.3% of the youths with high stress exposure had hurricane-attributable SED. Death of a loved one had the strongest association with SED among prehurricane residents of New Orleans, whereas exposure to physical adversity had the strongest association in the remainder of the sample. Among children with stress exposure, parental psychopathology and poverty were associated with SED. Conclusions: The prevalence of SED among youths exposed to Hurricane Katrina remains high 18 to 27 months after the storm, suggesting a substantial need for mental health treatment resources in the hurricane-affected areas. The youths who were exposed to hurricane-related stressors, have a family history of psychopathology, and have lower family incomes are at greatest risk for long-term psychiatric impairment. J. Am. Acad. Child Adolesc. Psychiatry, 2009; 48(11):1069-1078. © 2009 American Academy of Child and Adolescent Psychiatry.