Background: Plasma level of N-terminal pro-brain natriuretic peptide (P-NTproBNP) is a useful marker in prediction of mortality in peritoneal dialysis (PD) patients. However, the predictive value of spent dialysate counterpart (D-NTproBNP) of plasma NTproBNP on mortality and dropout is not known. Materials and methods: Simultaneous P-NTproBNP and D-NTproBNP assays were performed after an overnight dwell in 44 scheduled ambulatory PD patients. Patients were followed for similar to 47 months. Deceased patients or patients who were transferred to hemodialysis were regarded as dropouts. Results: 14 patients (31.8%) dropped out at similar to 4 years (9 deaths and 5 transfers to hemodialysis). Diabetics, males, and patients with higher membrane permeability had higher dropout rates. Patients with P-and D-NTproBNP higher than median values had higher mortality and dropout rates (Kaplan-Meier test, log-rank Test p < 0.05). Odds ratios of D-NTproBNP for death and dropouts were (3.807 (0.907-15.971), p = 0.068) and (2.87 (1.009-8.138) p = 0.048), respectively; odds ratios of P-NTproBNP for death and dropouts were (4.652 (0.914-23.693), p = 0.064) and (2.67 (0.924-7.716), p = 0.07), respectively; in ROC analysis for death, AUC for P-and D-NTproBNP were 0.762 (0.578-0.946, p = 0.016) and 0.765 (0.590-0.940, p = 0.015), respectively. Exclusion of diabetic patients from the analyses resulted in significant changes in the predictive value P-and D-NTproBNP. Although death and dropout rates were still higher in nondiabetic patients with higher NTproBNP levels, the differences between groups lost statistical significance. Conclusion: Both P-NTproBNP and D-NTproBNP are significant predictors of outcomes of interest. Predictive value of NTproBNP might be different in diabetics and non-diabetic CAPD patients.