Cancer genetics is creating new practice opportunities in medical genetics, oncology, and primary care. The ethical and counseling challenges of this new area of practice are not unique but sometimes take new form in the context of genetic risk. This article uses cases to explore the issues associated with shared family risk, including competing concerns of family members, duty to warn relatives of genetic risk, and testing of children and other relatives. The ethical obligations of clinicians start with the need to maintain competence in the face of rapidly evolving science. Clinicians should be able to identify patients within their practice who are candidates for genetic testing. When genetic susceptibility to cancer is identified, patients should be offered counseling and follow-up, with referral as appropriate, to ensure delivery of care consistent with current standards. When patients experience barriers to needed health care, clinicians should advocate for their needs. Clinicians must ensure the autonomy and informed decision-making of all members of cancer-prone families. Clinicians must also provide emotional support and accurate information about cancer risks and cancer risk reduction measures, including uncertainties. Teamwork among different specialties is important in addressing these challenges.