Objective: The comorbidity of schizophrenia and substance abuse is well documented and is remarkable for its prevalence and poor prognosis. While the etiology for this association is unknown, one possible mechanism relates to traumatic early life experiences, which have been shown to predispose individuals to both psychosis and substance abuse. Methods: Participants (N=122) who were outpatients in an inner city public mental health clinic and who were diagnosed with schizophrenia, were administered a battery of structured clinical assessments including the Childhood Traumatic Events Scale (CTES), Davidson PTSD rating scale, Hamilton Depression Rating Scale (HDRS), Positive and Negative Symptom Scale (PANSS), and assessments of medication satisfaction and side effects. Patients with schizophrenia and a history of substance abuse (N=70) were compared to patients with schizophrenia who did not have a history of substance abuse (N=52). Results: Patients with schizophrenia and a history of substance abuse had significantly higher frequency and severity of childhood traumatic events, greater PTSD symptomatology, significantly higher depression scores, and higher scores on the general subscale of the PANSS. Discussion: Our findings lend support to the notion that sensitization to stress from early life experiences may be a factor contributing to the high rate of substance abuse comorbidity in patients with schizophrenia.