Aims and methodA cross-sectional study aiming to assess the prevalence of trauma and post-traumatic stress disorder (PTSD) in a community substitution treatment sample, and to assess and compare the characteristics of traumatic experience, substance use, and psychological and social factors in those with and without PTSD. All assessments were completed during the interview which took approximately 1.5 h.ResultsThe prevalence for current PTSD was 26.2% and for lifetime PTSD 42.9%. Traumatic experiences were extremely common, with two or more reported by 92.9% of the sample. The two groups differed significantly on the majority of psychological functioning and social variables, with women experiencing higher rates of PTSD and the non-PTSD group having lower rates of psychological impairment.Clinical implicationsThe research supported findings from previous studies. The very high incidence of traumatic experiences has not been reported before. Training and information about trauma and PTSD for substance misuse workers are therefore necessary so that PTSD can be more easily detected and treated.