|Background: In this study, we assessed whether red blood cell distribution width (RDW) was associated with all-cause mortality in patients on peritoneal dialysis (PD) and evaluated its prognostic value. Methods: This study included 136 patients who had RDW levels at PD initiation from January 2007 to January 2014 at the Presbyterian Medical Center and Seoul St. Mary``s Hospital. We divided these patients into 2 groups (survivors vs. nonsurvivors), compared their clinical characteristics, and analyzed the predictors of survival. Results: The study included 79 men and 57 women, with a mean age of 54 years (range, 15e85 years). The mean follow-up duration was 32 months (range, 1e80 months). Of 136 patients, 14 died during the follow-up period. When clinical characteristics of survivors (n = 122) and nonsurvivors (n = 14) were compared, no differences were identified, with the exception of serum albumin, total iron-binding capacity (TIBC), left ventricular ejection fraction, total leukocyte count, and RDW value. Survivors had higher serum albumin (3.4 ± 0.5 vs. 3.0 ± 0.5 g/dL, P < 0.001) and left ventricular ejection fraction (56.8 ± 9.8 vs. 48.7 ± 12.8, P = 0.040) and lower TIBC (213.4 ± 40.9 vs. 252.8 ± 65.6, P = 0.010), total leukocyte counts (6.9 103/mL vs. 8.6 103/mL, P = 0.009), and serum RDW values (13.9 ± 1.7 vs. 16.0 ± 1.8, P < 0.001). Patients with high RDW levels ( 14.8) showed significantly higher all-cause mortality than patients with low RDW levels (< 14.8, P < 0.001). In multivariate-adjusted Cox analysis, RDW and TIBC at the start of PD were independent risk predictors for all-cause mortality. Conclusion: RDW could be an additive predictor for all-cause mortality in patients on PD.