Physicians whose patients may be affected by genetic cancer syndromes must be sensitive to a range of legal and ethical concerns. We provide an overview of the major issues, focusing on developments in the United States. The first section examines the physician's legal and ethical duties to the patient. A number of general rules are advanced, including: 1) genetic counseling should be offered to those considering genetic testing; 2) a genetic test should not be performed without the patient's informed consent; and 3) genetic information should not be disclosed to third parties without the patient's written authorization. Laws addressing genetic testing and disclosure of information are reviewed, as well as laws addressing genetic discrimination. Physicians must be aware that the availability of legal protections may affect a patient's willingness to undergo testing. Next, we examine the physician's duty to the patient's family. Where a conflict exists between the interests of the patient and the interests of family members, ethics and current law favor the interests of the patient, absent unusual circumstances. Further, we provide guidance on the scope of the physician's duty to inform, e.g., whether the physician must inform the patient of all medically reasonable treatment options, including those with which the physician disagrees. Finally, we discuss the special ethical and legal issues that prophylactic surgery raises. Areas covered include informed consent and insurance coverage. Several recent cases involving these issues are reviewed.