Recent reports indicate a decreased mortality risk for patients on chronic peritoneal dialysis in the United States. We sought to determine whether a higher use of automated versus continuous ambulatory peritoneal dialysis was associated with this improvement. Analyses were carried out using data from the United States Renal Data System on 66,381 incident patients on chronic peritoneal dialysis in the years 1996-2004 that were adjusted for demographic, clinical, laboratory and dialysis facility characteristics. Patients were followed until the time of transfer to other modes of dialysis, transplant, or death, whichever occurred first, or until their last follow-up through September 2006. Over time, the risks were substantially reduced such that the adjusted hazard ratios for death or technique failure of these patients in the 2002-2004 period were 0.55 (0.53, 0.57) and 0.62 (0.59, 0.64), respectively, compared with those of incident patients during the years 1996-1998. The risk improvements for both modes of dialysis were, however, found to be similar. Under intent-to-treat, time-dependent, and as-treated analysis, there was little or no difference in risk for death or in technique failure. Thus, the improved chronic peritoneal dialysis outcomes cannot be attributed to a greater use of automated peritoneal dialysis.