This study examined baseline correlates of substance use in the NIMH Clinical Antipsychotic Trials of Intervention Effectiveness project. Approximately 60% of the sample was found to use substances, including 37% with current evidence of substance use disorders. Users (with and without substance use disorders), compared with nonusers, were significantly more likely to be male, be African-American, have lower educational attainment, have a recent period of homelessness, report more childhood conduct problems, have a history of major depression, have lower negative symptom and higher positive symptom scores on the Positive and Negative Syndrome Scale, and have a recent illness exacerbation. Individuals with comorbid substance use disorders were significantly more likely to be male, report more childhood conduct problems, have higher positive symptom scores on the Positive and Negative Syndrome Scale, and have a recent illness exacerbation. These analyses suggest that substance use disorders in schizophrenia are especially common among men with a history of childhood conduct disorder problems and that childhood conduct disorder problems are potent risk factors for substance use disorders in schizophrenia.