Traumatic experiences and posttraumatic stress disorder (PTSD) are more frequent in patients with serious mental illness than in the general population. This study included 102 patients with schizophrenia, bipolar disorder, and schizoaffective disorder, according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria. Epidemiological and clinical data were collected using the Brief Psychiatric Rating Scale and Traumatic Life Events and Distressing Event questionnaires. We found a high number of traumatic experiences, and 15.1% of the patients met all criteria for PTSD. We found no differences based on diagnosis or sex, although there was a nonsignificant trend toward greater PTSD comorbidity in women. Among patients with serious mental illness and PTSD, 64.3% had made some attempt at suicide at some point in life, compared with 37.4% of patients without PTSD.