This study is part of an epidemiologcial investigation of mental health problems among patients in primary health care clinics in the Gaza Strip. It was conducted in 10 primary health care clinics selected at random, both amongst governmental and the main non-governmental primary health care providers. The objective of the study was to investigate the prevalence of PTSD among patients attending primary health care clinics in the Gaza Strip and the association between socio-demographic variables and PTSD. Every second patient in each clinic aged between 16 and 55 years, except those who came for referrals, vaccinations, insurance or driver's license examinations, prenatal care, reports, pregnancy problems, or emergencies, was approached and invited to participate. A total of 670 patients were asked to participate in the study, after consulting their general practitioner, with 661 agreeing to take part. It was found that the overall prevalence of PTSD symptoms in primary health care patients was 29 percent, and significantly higher among females than in males (P = 0.001). Prevalence of PTSD among those exposed to traumatic events was 36 percent. Highly educated patients were more often exposed to traumatic events, but the prevalence of PTSD was lower than among less educated patients. Males exposed to traumatic events reported a lower prevalence of PTSD than traumatized females.