Studies suggest that a majority of elderly patients would want to undergo cardiopulmonary resuscitation (CPR) if they had a cardiac arrest. Yet few studies have examined their preferences after clinicians have informed them about the outcomes of CPR. To study older patients' preferences regarding CPR, we interviewed as many ambulatory patients as possible in one geriatrics practice in Denver from August 1, 1991, through July 31, 1992. A total of 371 patients at least 60 years of age were eligible; 287 completed the interview (mean age, 77 years; range, 60 to 99). When asked about their wishes if they had cardiac arrest during an acute illness, 41 percent opted for CPR before learning the probability of survival to discharge. After learning the probability of survival (10 to 17 percent), 22 percent opted for CPR. Only 6 percent of patients 86 years of age or older opted for CPR under these conditions. When asked about a chronic illness in which the life expectancy was less than one year, 11 percent of the 287 patients opted for CPR before learning the probability of survival to discharge. After learning the probability of survival (0 to 5 percent), 5 percent said they would want CPR. Older patients readily understand prognostic information, which influences their preferences with respect to CPR. Most do not want to undergo CPR once a clinician explains the probability of survival after the procedure.