Background: The association of baseline blood pressure (BP) and mortality in incident peritoneal dialysis patients has not been adequately studied. Study Design: Cohort study. Setting & Participants: 2,770 patients on PD therapy at 180 days from start of renal replacement therapy in England and Wales between 1997 and 2004. Predictors: Systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP), and pulse pressure (PP) measured in the first 6 months of renal replacement therapy and other baseline demographic and laboratory variables. Outcomes: All-cause mortality was studied using time-stratified Cox regression models (to account for nonproportionality) dividing follow-up time into 4 intervals: year 1 (days 180 to 365), years 2 to 3, years 4 to 5, and years 6+. Interactions between BP components and transplant waitlist and diabetes status were explored. Results: Median follow-up was 3.7 years (range, 0.1 to 9.9 years), and 1,104 deaths were observed. In fully adjusted analyses, greater SBP, DBP, MAP, and PIP were associated with decreased mortality in the first year, but greater SBP and PP were associated with increased late mortality (in years 6+). However, in the subgroup of patients placed on the transplant waitlist within 6 months of starting renal replacement therapy, greater SBP, DBP, MAP, and PP were not associated with decreased mortality in the first year. Limitations: Exclusion of 3,086 patients because of missing BP data. No data were available for cardiac function or anti hypertensive medication. Conclusions: Although greater SBP, DBP, MAP, and PP appear protective against early mortality in the overall cohort, this effect is not seen in patients registered on the national transplant waiting list within 6 months of starting renal replacement therapy. Am J Kidney Dis 53:70-78. 0 2008 by the National Kidney Foundation, Inc.