Women with a psychiatric disorder who also abuse alcohol or other drugs have historically encountered barriers to integrated treatment for both disorders. Substance abuse treatment services and mental illness treatment services are usually organized independently of each other and few are designed to meet the needs of pregnant and parenting women. This chapter reviews the developmental histories of treatment systems for psychiatric and substance abuse disorders; the structural barriers that impede the delivery of services to individuals with co-occurring psychiatric and substance abuse disorders; the prevalence of dual disorders; issues related to diagnosis and assessment, types of diagnoses and addictions; treatment issues specific to women who are pregnant or parenting; models of service delivery; and initiatives directed at changing treatment systems.