Parental substance misuse places families at risk for involvement in Child Welfare Services (CWS) (Barth, Gibbons, & Guo, 2006). Furthermore, maltreated children of parents who misuse substances are more likely to misuse substances in adulthood than are maltreated children of parents who do not misuse substances (Schuck & Widom, 2001). More than 10% of all children in the United States live with a parent who misuses or is addicted to alcohol or drugs (Substance Abuse and Mental Health Services Administration, Office of Applied Studies, 2008). These children are disproportionately at risk for both poor developmental outcomes (Osborne & Berger, 2009) and being abused or neglected (Walsh, MacMillan, & Jamieson, 2003). They are also at risk for becoming involved with Child Protective Services and, potentially, for being removed from home and placed in substitute care if their home environment is deemed a threat to their safety. The child welfare system may be the locus of a vicious circle of intergenerational substance use. Maltreated children of parents who misuse substances will themselves be comparatively likely to misuse substances in adulthood (Schuck & Widom, 2001). Although CWS are intended, in part, to diminish maltreatment's negative impact on adolescents' substance use, there is evidence that receiving CWS affects adolescents' substance use adversely. Furthemore, experience in foster care or other out-of-home placement has been associated with substance misuse in adulthood (Zlomick, Tam, & Robertson, 2004). There is a dearth of literature on the extent and correlates of substance misuse among CWS-involved families, and the literature on prevention and treatment services is even more limited. Contributing to this gap in the literature is the fact that many child welfare journals fail to identify the role of substance abuse in child maltreatment. Furthermore, maltreated children continue to be a hidden population within the substance abuse literature. Scientists and practitioners interested in this area must sift through these two huge bodies of literature to find relevant studies. It is in this veritable Tower of Babel that social work can keep this crucial determinant of child safety, permanency, and well-being from becoming confounded. There is arguably no profession in the United States more closely identified with the field of child welfare than social work. Child welfare has even been referred to as a specialized field within social work, implying the professional preeminence, if not the exclusivity, of social work in delivering CWS (Lieberman, 1988). In addition, social workers play a huge role in substance abuse treatment and service delivery (Burke & Clapp, 1997). Therefore, social work may be one of the few professions to afford a comprehensive understanding of the interdisciplinary determinants, treatments, and prevention needs of families affected by substance misuse within the child welfare system. Social work has been criticized for many years as a profession that cherry picks theory and practice from allied fields, including psychology and sociology. Taking leadership in this area will allow the field of social work to demonstrate professional preeminence in an interdisciplinary area commonly overlooked by its critics. The following is an overview of the current state of the field of substance misuse and child welfare, followed by recommendations for epidemiological and social work services research inquiry. PREVALENCE OF SUBSTANCE MISUSE AND CHILD WELFARE INVOLVEMENT Although studies suggest that a sizable majority of families involved in CWS are affected by substance use, estimates of prevalence among parents and children vary widely. In its report to Congress in 1999, the U.S. Department of Health and Human Services (HHS) stated that between one-third and two-thirds of children in CWS were affected by substance misuse. To date, this is the only federally documented statistic related to substance use and CWS. …