A patient who refuses to notify their relatives of potential at-risk status brings a genetics provider to face conflicting ethical principles and ill-defined legal precedent. Genetics professionals' views on the disclosure of patient information to at-risk relatives have remained largely unexamined. Prior analyses have been limited to identifying factors contributing to genetics providers' self-predicted responses in hypothetical scenarios. Our group was the first to examine the clinical experience of genetic counselors with this issue [Dugan et al., 2003]. We report here results from our follow-up survey of medical geneticists who are members of either the American Society of Human Genetics and/or American College of Medical Genetics in an effort to identify their experiences in warning at-risk relatives and the factors driving their decision-making processes. Over two-thirds of medical geneticists surveyed (69%, 143/206) believe they do bear responsibility to warn their patients' relatives when found to be at-risk for genetic disease. One-quarter (25%, 31/123) of medical geneticists who faced the dilemma of a patient refusing to notify their at-risk relatives seriously considered disclosure to those at-risk relatives without patient consent. Only four respondents proceeded to warn at-risk relatives of their status. Whereas genetic counselors cited emotional issues as playing a primary role in their decision not to warn, medical geneticists identified patient confidentiality, eventual case resolution by other means, and legal liability as the major factors leading to non-disclosure in 76% of actual scenarios. Responsibilities of medical geneticists, genetic counselors, and non-genetics healthcare professionals facing this issue will need to be more clearly defined to provide optimal medical care within the bounds of acceptable practice. © 2003 Wiley-Liss, Inc.