Physicians treating newly incapacitated patients often must help navigate surrogate decision-makers through a difficult course of treatment decisions, while safeguarding the patient's autonomy. We offer guidance for intensive care physicians who must frequently address the difficult questions concerning disclosure of confidential information to surrogates. Three clinical vignettes will highlight the ethical challenges to physician disclosure of a critically ill patient's HIV status. Two key distinctions are offered that influence the propriety of disclosure: first, whether HIV infection represents a 'primary cause' for the patient's critical illness; and second, whether the surrogate may be harmed by failure to disclose HIV status. This balanced consideration of the direct duties of physicians to patients, and their indirect duties to surrogates and third-party contacts, may be used as a framework for considering other ethical obligations in the intensive care unit. We also provide a tabulation of individual US state laws relevant to disclosure of HIV status.