The estimated prevalence of serious emotional disturbance (SED) among children and adolescents exposed to Hurricane Katrina 18 to 27 months after the storm is approximately 15 percent. More than 80 percent of the children in the study sample were exposed to at least one hurricane-related stressor, and stress exposure was associated strongly with SED. Twenty percent of the youths with high stress exposure had hurricane-attributable SED. The 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. The results of the study demonstrate that mental health problems among the youth exposed to Hurricane Katrina are common and widespread. A substantial need is demonstrated for youth mental health services in New Orleans and other affected Gulf Coast areas. The effects of Hurricane Katrina on New Orleans and affected Gulf Coast areas were unprecedented. In the first 3 to 6 months after a hurricane, more than 50 percent of children exposed to the disaster exhibit symptoms of posttraumatic stress disorder (PTSD), disruptive behavior, or other psychological manifestations. The objective of this study was to estimate the prevalence of 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. A sample of prehurricane residents of areas affected by Hurricane Katrina was administered in a telephone survey. Respondents provided information on up to 2 of their children (n=797) aged 4 to 17 years. Tables and references