Objective: To explore the relationship between posttraumatic stress disorder (PTSD) in flood victim parents and children in Hunan, China.Methods: Using the method of multistage cluster random sampling, we conducted a retrospective investigation on 3,698 families in Hunan, China who suffered from flooding in 1998. Investigators held face-to-face interviews with the parents and children of the families. The diagnosis of PTSD was made according to the criteria of the Diagnostic and Statistical Manual of Mental Disorders, fourth edition.