The 1996 Peritoneal Dialysis-Core Indicators Study (PD-CIS) retrospectively reviews a random sample of peritoneal dialysis patients from the United States End-Stage Renal Disease (ESRD) program. Peritoneal dialysis (PD) patients are more likely to have a primary diagnosis of glomerulonephritis, less likely to be of African-American heritage, and are younger than hemodialysis patients. One third of PD patients now perform some form of automated peritoneal dialysis (APD) rather than continuous ambulatory peritoneal dialysis (CAPD). The dialysis prescriptions currently employed do not appear to be based on kinetic principles, and the intensity of dialysis achieved is below the proposed minimal guidelines for 30% of patients. In 1996, the mean dialysis index or wKt/Vurea for CAPD patients was 2.0 +/- 0.5 and was not significantly altered from the 1995 value of 2.1. Eighty-four percent of CAPD patients perform four or fewer exchanges daily, and only 27% of patients have prescriptions using infusion volumes greater than 2 L. Although hematocrits have improved since 1995, 30% of PD patients have a hematocrit below 30%. The mean serum albumin for PD patients is 3.5 g/dL, and 25% of patients have a 6-month average serum albumin value below 3.2 g/dL. In general, the indices monitored as predictive of health and well-being of PD patients afford significant opportunity for improvement.