A statewide sample of 1735 Iowa residents, approximately half of whom were victims of the 1993 Midwest Floods, participated in interviews 1 year prior to, and 30 to 90 days after, the disaster. Employing a rigorous methodology including both control-group comparisons and predisaster assessments, we performed a systematic evaluation of the disaster's impact. Overall, the disaster led to true but small rises in depressive symptoms and diagnoses 60-90 days postflood. The disaster-psychopathology effect was not moderated by predisaster depressive symptoms or diagnostically defined depression; rather, predisaster symptoms and diagnoses uniquely contributed to increases in postdisaster distress. However, increases in symptoms as a function of flood impact were slightly greater among respondents with the lowest incomes and among residents living in small rural communities, as opposed to on farms or in cities. Implications for individual- and community-level disaster response are discussed.