The effect of mothers' participation in substance abuse treatment on reunification with their children who are in out-of-home care is an important policy issue. This article examines the predictors of child reunification among mothers who participated in a statewide treatment outcome study. Data were integrated from multiple sources to determine the contributions of characteristics of mothers (n = 1,115), their children (n = 2,299), and treatment programs (n = 43) on reunification outcomes. Hierarchical linear modeling was used to determine the fixed and random effects of mother, child, and program characteristics. Mothers with more employment and psychiatric problems were less likely to be reunified with their children; completion of 90 or more days in treatment approximately doubled their likelihood of reunification. Mothers who were treated in programs providing a "high" level of family-related or education/employment services were approximately twice as likely to reunify with their children as those who were treated in programs with "low" levels of these services.