Physicians and patients share a common interest in clarifying and maximizing the powers and protection of advanced directives for future care in the event of patient incompetence. Although the complexity and unpredictability of health care circumstances make it impossible to guarantee complete control over therapeutic measures to be used when survival is in question, physicians should offer their patients the opportunity to reflect on their values and wishes and to express them explicitly. The ideal advanced directive should clearly state the author's intentions; contain clear documentation regarding authorship; be flexible, allowing family and caregivers to respond appropriately to changing circumstances; be available when needed; and be supported by legal powers that grant patients the right of enforcement and grant health care providers protection from liability. Advanced directives can be set as instruction directives or proxy directives, each form having advantages and disadvantages.