Research from Canada and the United States suggests that not offering dialysis to patients who might benefit still occurs. This study was conducted to investigate nonreferral and nonacceptance to dialysis by primary care physicians (PCPs) and nephrologists in these countries. We surveyed a random sample of Canadian and US PCPs and nephrologists concerning their attitudes toward and experience with withholding dialysis in patients with advanced chronic renal failure. In response to a question about whether the physician believes there should be an age beyond which dialysis should not be offered, 12% of Canadian PCPs, 20% of US PCPs, 4% of Canadian nephrologists, and 9% of US nephrologists answered yes. When asked about their recommendations concerning dialysis initiation in 10 vignettes of patients with impending end-stage renal disease (ESRD), the responses of Canadian and US physicians were similar. PCPs compared with nephrologists were less likely to recommend dialysis in cases with physical illnesses and more likely to recommend it in cases with neuropsychiatric impairments. Over a 3-year period, 13% of Canadian PCPs and 19% of US PCPs reported nonreferral to dialysis at least once. Withholding rates were 25% for Canadian PCPs, 16% for US PCPs, 13% for Canadian nephrologists, and 17% for US nephrologists. We conclude that although nonreferral of patients who might benefit from dialysis still occurs, it does not seem to be common, and the attitudes of Canadian and US physicians toward this issue are similar and could not entirely account for the much greater incidence of treated ESRD in the United States. PCPs and nephrologists should continue to be educated about the modern criteria for patient selection for dialysis.