An important principle of practice for both agencies is that the safety of victims is paramount. The authors recommend that the perpetrator of the sexual abuse be removed from the family home until the ongoing risk issues and safety needs of all family members are determined. Statutory child protection mandates and police involvement are often warranted to ensure safe outcomes for all concerned. The challenge for both agencies has been to achieve the best outcomes for families in a situation that is fraught with dilemmas and difficulties for all involved. For the professionals involved, one of the greatest challenges is obtaining knowledge about sibling sexual abuse as a particular type of sexual offending. Both experience and the literature indicate that a combination of individual and group treatment for the children concerned, individual and/or conjoint therapy for parents/caregivers, and family therapy at a later point in the process are all part of the ideal therapeutic process. Family therapy can provide an opportunity to explore the following issues: other siblings' understanding of what has occurred and how they are coping; the lines of loyalty drawn within the family and by whom; the general level of sibling violence within the family; the incidence of other abuse between family members; the availability of parents both physically and emotionally; the parents' own sibling relationships; and the acceptance or otherwise of treatment for both the victim and the young abuser. It is not unusual for the therapy process to last up to 2 years. The paper concludes with a discussion of challenges for future practice. The authors recommend that sibling sexual abuse be acknowledged as a serious community problem; that professionals focus on early identification of children at risk of sexually abusive behaviors; that there be collaboration among child protection, police, and legal systems; that practice standards for agencies responding to such cases be developed; and that lessons learned from practice be incorporated in ongoing research designed to assist in preventing sexual abuse. 8 references and two case studies