Background and Rationale: ICU clinicians regularly care for patients who lack capacity, an applicable advance directive, and an available surrogate decision-maker. Although there is no consensus on terminology, we refer to these patients as "unrepresented." There is considerable controversy about how to make treatment decisions for these patients, and there is significant variability in both law and clinical practice.Purpose and Objectives: This multisociety statement provides clinicians and hospital administrators with recommendations for decision-making on behalf of unrepresented patients in the critical care setting.Methods: An interprofessional, multidisciplinary expert committee developed this policy statement by using an iterative consensus process with a diverse working group representing critical care medicine, palliative care, pediatric medicine, nursing, social work, gerontology, geriatrics, patient advocacy, bioethics, philosophy, elder law, and health law.Main Results: The committee designed its policy recommendations to promote five ethical goals: 1) to protect highly vulnerable patients, 2) to demonstrate respect for persons, 3) to provide appropriate medical care, 4) to safeguard against unacceptable discrimination, and 5) to avoid undue influence of competing obligations and conflicting interests. These recommendations also are intended to strike an appropriate balance between excessive and insufficient procedural safeguards. The committee makes the following recommendations: 1) institutions should offer advance care planning to prevent patients at high risk for becoming unrepresented from meeting this definition; 2) institutions should implement strategies to determine whether seemingly unrepresented patients are actually unrepresented, including careful capacity assessments and diligent searches for potential surrogates; 3) institutions should manage decision-making for unrepresented patients using input from a diverse interprofessional, multidisciplinary committee rather than ad hoc by treating clinicians; 4) institutions should use all available information on the patient's preferences and values to guide treatment decisions; 5) institutions should manage decision-making for unrepresented patients using a fair process that comports with procedural due process; 6) institutions should employ this fair process even when state law authorizes procedures with less oversight.Conclusions: This multisociety statement provides guidance for clinicians and hospital administrators on medical decision-making for unrepresented patients in the critical care setting.