The many challenges to effective physician-patient communication and decision-making become even more intractable when patients are unable to make decisions for themselves. In ideal circumstances, patients can provide information about their preferences directly, but if the patient has lost the ability to make some or all medical decisions, physicians must try to figure out what the patient would choose based on advance directives, conversations with family members or surrogate decision-makers, and the context of the patient’s known values and goals. Under this approach, the ideal is to make decisions that respect the patient’s preferences even when he can no longer articulate them.