We compared the understanding by family physicians and nurses of their elderly outpatients' preferences for cardiopulmonary resuscitation and mechanical ventilation under 3 scenarios reflecting varying qualities of life. Physicians and nurses correctly predicted patients' treatment preferences in from 59% to 84% and 53% to 78% of cases, respectively, for the various decisions. For most decisions, neither physicians nor nurses were significantly more accurate in their predictions than expected by chance alone. Moreover, nurses and physicians did not significantly agree with one another in their predictions of patients' preferences for any of these decisions. These results suggest that while nurses' and physicians' perceptions of patients' preferences for life-sustaining treatment are not necessarily similar, neither nurses nor physicians systematically understand their elderly patients' resuscitation preferences.