We performed a national survey to explore the circumstances under which general internists and nephrologists discuss cardiopulmonary resuscitation (CPR) with patients and the factors influencing physician decisions to open such discussions. We wondered whether nephrology fellowship training and/or formal exposure to an ethics course during training altered physicians' use of CPR. Significantly more nephrologists than internists responded to the study (nephrologists, 174/467; internists, 92/380; P less than 0.01). Few of the respondents participated in an ethics course during training (9% of nephrologists, 15% of internists; P = NS), and fewer than half (26% of nephrologists, 37% of internists; P = NS) had engaged in formal discussions about initiating and withdrawing life-sustaining treatment during their training. Nephrologists spent significantly more time caring for patients in intensive care units (ICUs) (29% v 21% of time, P less than 0.05), and more often discussed CPR during their first meeting with a patient (7% of nephrologists v 1% of internists; P less than 0.05). Twenty-eight percent of nephrologists and 19% of internists thought CPR should be offered to all patients. Both nephrologists and internists rated neurologic dysfunction as the most important and age the least important factor influencing decisions to terminate CPR. Nephrologists were less comfortable than internists with healthy dialysis patients' decisions to refuse CPR. We conclude that nephrologists are more inclined than internists to use CPR in dialysis patients, in patients with impaired functional status, and in all patients. Training in medical ethics did not account for the differences among nephrologists and internists.