Competence frequently becomes an issue when a patient refuses a recommended surgical procedure or medication, refuses a placement option such as a nursing home or threatens to leave the hospital against medical advice. Physicians often struggle to balance the patient's right to self-determination and informed consent with their own mission to provide patients with optimal treatment. At present, few guidelines exist to assist physicians in making competence determinations. Legal precedents and conceptual issues in evaluating competence are reviewed. A protocol for assessing competence is presented.