Objective: To study the influence of residual renal function (RRF) on different parameters of the renal substitutive treatment offered by peritoneal dialysis. Methods: We analyzed the impact of RRF on dialysis dose, nutrition parameters, anemia and phosphocalcic metabolism in 37 patients with end-stage renal disease (ESRD) treated by continuous ambulatory peritoneal dialysis (CAPD). Analytical controls were done every 6 months after an initial assessment at the end of the first month of treatment. Multiple lineal regression models were used as the statistical method to analyze the influence of RRF on different theoretically dependent factors. RRF was calculated as a mean of creatinine and urea clearances. Three observations per patient were used: one at the end of the first month of treatment; a final one at the end of follow-up (mean time 24.2 ± 11.4 months), and at a mean time between them (13.4 ± 6.7 months), with a final number of 111 observations. Results: Dialysis dose: RRF was the most important factor in terms of creatinine clearance (r<sup>2</sup> = 0.94; β = 0.999), KT/V (r<sup>2</sup> = 0.68; β = 0.819) and β<sub>2</sub>-microglobulin levels (r<sup>2</sup> = 0.46; β = –0.489). Nutrition parameters: RRF was a determinant factor for normalized protein catabolic rate (r<sup>2</sup> = 0.53; β = 0.471), percent lean body mass (r<sup>2</sup> = 0.45; β = 0.446) and albumin levels (r<sup>2</sup> = 0.25; β = 0.229). Anemia: RRF was the most important factor when studying hemoglobin levels (r<sup>2</sup> = 0.28; β = 0.407). Phosphocalcic metabolism: Between the analyzed factors, RRF was the only one which reached significance on serum phosphate levels (r<sup>2</sup> = 0.19; β = –0.594). RRF did not show any relationship with either calcium or PTH levels. Conclusions: Independent of other factors, RRF in CAPD is positively and directly related to dialysis dose, β<sub>2</sub>-microglobulin levels, nutrition parameters (albumin, normalized protein catabolic rate and percent lean body mass, hemoglobin and serum phosphate levels.