Consideration of residual kidney function (RKF) is crucial in formulating a peritoneal dialysis (PD) prescription. The current standards of adequacy call for a total delivered dose of PD equivalent to a weekly K_prt/V > 1.7, where p and r denote peritoneal and renal contributions respectively. RKF, together with the patient’s body mass and peritoneal solute transport rates, determine adequacy of PD given a specific prescription. It is thus pertinent to review the expected rate of RKF loss in PD and in different disease states, its contribution to total solute clearance in clinical series, its equivalency to peritoneal clearances and practical methods for its measurement.