Objectives: To estimate the current prevalence of posttraumatic stress disorder (PTSD) and the diagnosis rate of this disorder ascertained by psychiatrists in training. Methods: We interviewed 200 adults under treatment in a university mental health outpatient clinic. The PTSD diagnoses obtained using the Structured Clinical Interview for DSM-IV (SCID-IV) were compared with the patients’ medical records. Results: Forty-one patients (20.5%) were diagnosed with current PTSD, but only one of them (2.4%) had previously received this diagnosis. This study confirms that although PTSD is highly prevalent among mental health outpatients, it is remarkably underdiagnosed in teaching hospitals. Conclusions: These findings suggest that psychiatrists in training may be failing to investigate traumatic events and their consequences and strongly indicate that trauma-related issues should be given more prominence in psychiatry curricula and psychiatrist training.