Objective: The aim of this study was to describe the prevalence of symptoms consistent with post-traumatic stress disorder (S-PTSD) in police personnel involved in rescue operations after the AZF chemical plant explosion in Toulouse, France, on September 21, 2001, and the relationship between S-PTSD and the type of rescue operation. Design: A cross-sectional survey was performed, using a mailed questionnaire. Participants: Six hundred and thirty-five out of 1,500 rescue operations police officers participated in the study. All were involved with the explosion site after the industrial disaster. Main outcome measure: The outcome variable was the presence of S-PTSD. The explanatory variables were the level of exposure during the rescue tasks. Statistics: Logistic regression was used to calculate the adjusted odds ratios (OR). Results: The prevalence of S-PTSD among policemen was 4.1 percent [95% CI: 2.1-6.2]. Policemen who had immediate health consequences (OR 4.6; [95% CI: 1.3-16.4]) and those who provided medical assistance to the victims (OR 5.7; [95% CI: 1.6-20.2]) had a higher prevalence of S-PTSD. Conclusions: Providing medical assistance to the victims was a major risk factor of S-PTSD for police officers. Training police officers to take part in medical activities at the time of the disaster might lead to a reduction of SPTSD incidence in this group. (R.A.)