Ethicists and lawyers agree that competent adult patients or their surrogate decision-makers have the right to forego life-sustaining treatment, but the views of practicing physicians have not been well-studied. To examine nephrologists' experience with and attitudes towards decisions to forego dialysis, a questionnaire was sent to all 161 nephrologists performing chronic dialysis in six New England states; 118 (73%) responded. The proportion of nephrologists who reported withholding (not starting) dialysis from the cited numbers of patients during the previous year was 11%, 0; 58%, 1 to 5; 20%, 6 to 10; 8%, 11 to 15; and 3%, greater than or equal to 16. For withdrawing (stopping), the proportions were 19%, 0; 73%, 1 to 5; 9%, 6 to 10; and 0%, greater than or equal to 11. The nephrologists withheld dialysis more times than they withdrew it (chi 2 = 26; P = 0.004). If requested to do so by a competent patient, 88% of nephrologists would stop dialysis. If requested by the family of an incompetent patient, 90% would stop if the patient had clear prior wishes, but only 63% would stop if prior wishes were unclear. With competent patients, the issue of withdrawal of dialysis was usually raised by the patient (56%). With incompetent patients, the issue was raised by the family (42%) or nephrologist (30%). It was concluded that decisions to withhold dialysis are more frequent than decisions to withdraw it. Moreover, nephrologists agree about the management of requests to withdraw dialysis in competent patients or incompetent patients with clear prior wishes; they disagree about the management of incompetent patients with unclear prior wishes.(ABSTRACT TRUNCATED AT 250 WORDS)