The passage of the federal Adoption and Safe Families Act (ASFA), which calls for timely permanency planning for children placed into state foster care systems, has led to increased attention to the need for timely and appropriate treatment services to families with substance abuse issues who are involved with child welfare. Using statewide administrative data collected before and after the implementation of ASFA, the present study explores the influence of ASFA, as well as other family characteristics, on patterns of treatment service utilization by child-welfare involved clients. Findings suggest that in the period following the ASFA legislation, mothers entered substance abuse treatment significantly more quickly after the start of their child welfare cases, and remained in treatment longer, compared to pre-ASFA. No differences in rates of treatment completion were found. Results are interpreted in terms of the changing treatment service context, enhanced collaboration between child welfare and treatment systems, and the possible influence of the legislation on parents' motivation to enter treatment