In this paper the incidence and the course of flood-related PTSD in the rural population of the southwest part of Poland will be presented. To serve this purpose, four villages located in the Nysa Klodzka basin were chosen. In 1997 these locations were devastated by the disaster unexpectedly and in considerable degree. The study included 97 eyewitnesses of the flood who had never had any need to seek psychiatric help before the disaster and who had not reported any other significant stressful life events which could have been accounted for the PTSD. The intensity, risk and duration of trauma for all subjects were the same. None had received any psychological or psychiatric support after the flood. The examination took place 60-63 months after the event and was conducted by one trained psychiatrist at the homes of those affected after prior phone appointment. The interview was based on the Composite International Diagnostic Interview (CIDI), section A (sociodemographic data) and section N (PTSD symptoms). PTSD was diagnosed in 30.9% of those interviewed. Individuals displaying PTSD symptoms were mainly unemployed (39.2% of unemployed individuals had PTSD), with low educational level (42.9% of subjects with primary education had PTSD) and older. Men were more often affected (39.5%) than women (25.4%) and it proved to be associated with their low level of education and poverty. In 15.5% of those interviewed fully developed PTSD was still present 60-63 months after the flood. The characteristics and patterns of PTSD occurrence observed in the examined population are in concordance with world literature. Low level of education and low economic status of men could account for the high rate of PTSD diagnosis in this group rather than in women. None of the examined subjects confirmed having had short-lasting (less than a month) symptoms which precluded the diagnosis of acute stress reaction. This was probably due to the durability of the devastation caused by the flood and prolonged exposure to a chronic stressor