Purpose: To explore the relationship between the sibling status of children in substitute care (e.g. presence of other siblings in care, presence of other siblings in the same placement) and the likelihood of several distinct substitute care outcomes, including both permanency (e.g. adoption, reunification) and pre-permanency (e.g. placement instability) outcomes. Methods: Administrative data from the Illinois Department of Children and Family Services regarding all placements between 1995 and 2001 (N=42,567) were matched with census records, foster parent criminal background check data, state wage data, and Medicaid paid claims records. Because the observed relationships between placement with siblings and the disposition of child welfare outcomes are likely confounded by selection effects and endogeneity, all outcomes were analyzed with recursive, simultaneous-equation models for discrete outcome data (Burnett, 1997). Such an approach allowed for the explicit modeling of the effect of placement with siblings on the outcomes of interest. Control variables included data pertaining to the characteristics of children (e.g. demographics; health, disability, and mental health diagnoses; substitute care history), foster parents (e.g. demographics, wage income, household size, license type), and child welfare agencies (e.g. organizational structure and resource environment, characteristics of case workers). Results: A majority of children (64%) in the sample had siblings who were also placed in care. Approximately 61 % of children with concomitantly-placed siblings were placed in the same facility or foster home with at least some of their siblings. The results of the multivariate analyses reveal that, when considered simultaneously, the relationships between sibling status and child welfare outcomes are complex. For instance, although the presence of siblings in care was associated with an increased probability of experiencing several adverse outcomes (e.g. placement instability, run away), concomitant placement with one or more siblings was found to exert a countervailing influence, which in some cases exceeded the main effect of siblings in care. Moreover, when analyzed in conjunction with other placement characteristics, including placement with relatives and/or placement within the same community as a child's home or record, a broader finding regarding the ameliorative effect of kin and community emerged. Implications: These results suggest that, when children are placed in care with siblings, placement of siblings in the same facility or home can exert a powerful effect on the outcomes experienced by children. These findings, although somewhat intuitive, have important practice and policy implications for child welfare. Most directly, they support the argument that placement with siblings, especially in cases where relative placements are not possible, should be a primary criterion upon which potential placements are judged. Further, in conjunction with the findings concerning other placement characteristics, they suggest that increased efforts be made to locally recruit and support relative and non-relative foster homes willing to accept sibling sets. More generally, these findings suggest that siblings may benefit from being able to have "shared" experiences of their time in care, examples of which include enrollment in the same school or daycare, sibling-focused group therapy, sibling visitation, and assignment of the same case worker to all siblings.