Studied the effect that different frequencies of occurrence of posttraumatic stress disorder (PTSD) symptoms would have on the prevalence rate of PTSD as part of a prospective study of the Lebanon Wars. Data were analyzed from 234 18-65 yr olds, from 2 communities living in Beirut, Lebanon that remained during the followup period. Ss were first asked about the occurrence of different war events and then about various symptoms of PTSD that followed each of those specific events. War events were assessed using the war events questionnaire. The probing on the frequency of occurrence of symptoms was done by determining the time of onset and offset of each symptom, the number and length of occurrence per wk. Results showed that the prevalence of PTSD decreased by half if symptoms were required to have occurred at least twice per wk. This phenomenon was true whether war or nonwar traumata was considered and was also true for the Diagnostic and Statistical Manual of Mental Disorders-III-Revised (DSM-III-R) and the Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV) definitions of PTSD.