The necessity of surrogate decision making arises for geriatric patients who can no longer make decisions for themselves. Almost every clinical situation involves some assessment of a patient's decisional capacity. Because decisional capacity is decision specific and entails the ability to manipulate information, it is best to conduct functional evaluations and use psychiatric measurements for dementia cautiously in determining decisional capacity. Traditionally, the medical community has relied on family members to be surrogate decision makers when a patient is assessed as decisionally incapacitated. That practice still has moral warrant, even amid advocacy for the use of advance directives, because most people have not completed such planning instruments. The family as a primary social unit is likely the most concerned for the welfare and wishes of the patient. These theoretical grounds are supplemented by emerging empirical evidence that elderly patients themselves almost always prefer that family members serve in the role of surrogate decision makers. Dealing with family surrogates obliges the geriatrician to ensure that failures in communication do not arise and that conflicts of interest are avoided in protecting the best interests of the patient. Although recent legal climate has shown a preference for a substituted judgment standard in surrogate decision making, medical concern for the best interests of the patient, together with empirical evidence that the elderly are most interested in decisions that arise out of trusted interdependencies, suggests that rules and laws are no substitute for the good faith human actions of trusted surrogates.