In the past decade, peritoneal dialysis use among patients with end-stage renal disease has declined in many countries. Studies from the United States indicate that many academic centers do not have adequate resources to train fellows, most incident dialysis patients are not offered peritoneal dialysis, and more than half of dialysis clinics do not have the infrastructure to support peritoneal dialysis. Some are concerned that the outcomes of peritoneal dialysis and maintenance hemodialysis patients may not be equivalent, a notion that is not supported by outcome studies. Given the effect of modality selection on patients' lifestyle, attempts to conduct a randomized, controlled comparison of maintenance hemodialysis and peritoneal dialysis have been unsuccessful. Most observational studies showed that peritoneal dialysis is associated with a survival advantage that diminishes over time; it is unclear whether any of the differences over time are attributable to the modality. Between 1996 and 2003, the early outcomes of peritoneal dialysis patients further improved, whereas those for maintenance hemodialysis patients remained unchanged. Differences in outcomes may be due to residual statistical confounding; however, several biologic mechanisms can be postulated: The early survival advantage may be related to the better preservation of residual renal function with peritoneal dialysis, and the diminution of the survival advantage may be related to worsened volume control. There is a need for large observational and interventional studies among peritoneal dialysis patients to sustain and enforce the improvements in both dialysis therapies.