Directors of residential agencies for persons with intellectual disability in one U.S. state completed a self-administered, mailed survey to assess relative importance of information sources and decision factors in proxy healthcare decision-making. The most important sources were physician recommendations and input from the person; family input, care staff recommendations, and medical records were less valued. The person's wishes and best interests and recommendations of medical experts were the most important decision factors. Less important were benefits and risks of the intervention, family wishes, and health status; little emphasis was accorded to religious affiliation and extra cost to agency. More research is needed on how best to elicit the wishes and determine what constitutes the "best interests" of these vulnerable individuals.