The results showed that the mothers in substance abuse treatment who were involved with child welfare services were younger, had more children, and had greater economic difficulties than the substance abusing mothers not involved with child welfare. Additionally, the mothers involved with child welfare services were more likely to have a history of physical abuse and to be referred by the criminal justice system to treatment in outpatient programs. The mothers involved with the child welfare system had lower levels of alcohol severity, but they had disproportionately high rates of methamphetamine abuse. The two groups of mothers in substance abuse treatment did not differ in terms of psychiatric severity or criminal involvement. The findings suggest that mothers involved with the child welfare system enter substance abuse treatment through different means and present a different clinical profile than other substance abusing mothers. Treatment needs of mothers involved in child welfare extend to treatment for physical abuse, economic difficulties, and criminal justice involvement. Data were drawn from the California Treatment Outcome Project, a statewide outcome monitoring system that tracks client movement through the treatment programs. The current analysis involved 1 group of 1,939 mothers of children less than 18 years of age who were involved with the child welfare system and 1 group of 2,217 mothers of children less than 18 years who were not involved with the child welfare system. Clients were assessed at treatment intake with the Addiction Severity Index. Data analysis techniques involved bivariate and multivariate logistic regression analyses. Future studies should focus on linking parent treatment participation with child welfare outcomes. Tables, references