This paper discusses the interagency collaboration between a clinical assessment and intervention program for toddlers offered through the psychiatry department of a large metropolitan west coast medical center and a group home for infants and young children who are positive for the human immunodeficiency virus (HIV). The paper presents the case of a developmentally at-risk 2-year-old whose mother and twin brother were HIV-positive. The healthy toddler resided in the group home with his sick twin and was cared for by staff there, and the staff social worker contacted the early intervention program for assistance with the boy's behavior and communication skills. Agency staff in the group home for HIV-positive children took on the role of surrogate parents. One caregiver attended early intervention group sessions and another caregiver participated in home visits. The paper points out problems in working effectively with multiple caregivers having different levels of knowledge about developmental issues and varying degrees of tolerance for the boy's negativistic behavior. The main treatment goal was to help the boy's caregivers appreciate his need for a significant attachment relationship with them. Intervention areas also focused on helping his caregivers to actively prepare him for change, facilitate his transitions, and acknowledge his emotional experiences. (JDD)