Results indicated that the 3-month intervention was more cost-effective than the 9-month intervention in relation to positive changes in risk and protective factors in child safety. However, cost-effectiveness analysis indicated that the 9-month intervention was more cost-effective than the 3-month intervention in relation to improved unit changes in the child's behavior between baseline and 6 months after service closure. Families served in both FC3 and FC9 groups demonstrated significant positive improvements in risk and protective factors in child safety over time. Because the 3-month intervention cost less to deliver, the FC 3 intervention appeared more cost-effective in relation to positive changes related to the primary targets of the intervention; however, when applying more detailed cost-effectiveness analysis to the one area of difference between groups, the FC9 intervention was more cost-effective in relation to unit changes in child behavior. The cost-effective ratio for the FC9 group compared to the cost-effective ratio for the FC3 group indicated a lower cost for each improved unit change in the child's behaviors measured by the Child Behavior Checklist. Data were collected from a sample of 154 families with 473 children in a poor, urban neighborhood; those meeting risk criteria for child neglect were randomly assigned to receive either a 3- or 9-month intervention. Child protective service reports, self-report, and observational data were analyzed. Figure, tables, references