During 1981–1984, at our center 6/75 patients on CAPD and 1/86 on HD demonstrated a recovery of renal function. This and the observation that diuresis was maintained on CAPD, led us to study urine output (UO) and creatinine clearance (CrCI) in 41 patients on CAPD (CAPDp) and 45 on HD (HDp) without the use of diuretics. CAPDp had a decline in diuresis from 1201 ± 379 mI/day to 731 ± 572 (p < 0.01). HDp diuresis decreased from 1233 ± 439 to 438 ± 568 (p < 0.01). Creatinine clearance: HDp 5.8 ± 1.6 ml/min before, 1.3 ± 1.5 after; CAPDp 6.4 ± 2.0 before, 3.9 ± 2.9 after. After one year, HDp showed a significant drop in diuresis; three years passed before CAPDp had significant drop. Patients with glomerulonephritis showed the same trend on HD and CAPD. CAPDp with interstitial nephropathy had a smaller mean annual decrease in UO and CrCI, compared to HDp. CAPDp with nephroangiosclerosis showed less decrease in diuresis compared to HDp. These data confirm that, com pared to HD, CAPD treatment maintains residual renal function even in patients not using diuretics, and suggest that CAPD is a treatment of choice for those considered likely to recover renal function. Some workers have reported a slow decline in residual renal function and diuresis in patients on CAPD (1,2,3). Rottembourg (1), in particular, suggests that diuretics may have helped his patients to maintain diuresis. In 161 dialyzed patients (75 on CAPD, 86 on HD) who started dialysis between 1981 and 1984, six CAPD patients recovered renal function but only one HD patient. This disparity led us to inquire whether when compared to HD, CAPO enables us to maintain satisfactory, long-term diuresis, without the use of diuretics.