The influence of ethnicity on peritoneal permeability and the adequacy of peritoneal dialysis was studied in 202 end-stage renal failure patients on peritoneal dialysis, Patients were classified into whites, Orientals, blacks, and a miscellaneous group consisting of East Indians, Persians, and others whose ethnicity was unknown, The patients were on peritoneal dialysis for a mean period of 29.1 +/- 15.8 months before the study, All patients underwent a peritoneal equilibration test with 24-hour urine and dialysate collection. The kinetic parameters were calculated using commercial software (PD Adequest; Baxter Healthcare, Round Lake, IL), The mean volume of exchange, weekly KW, and weekly creatinine clearance were comparable in the different ethnic groups, but the normalized protein catabolic rate was significantly higher in the Orientals (P = 0.03), The high transporters tended to be males with a large body surface area and in the older age group, The low transporters achieved a higher Kt/V than those in the other transport groups (2.3 +/- 0.4 v 2.06 +/- 0,52; P = 0.015). The women had a significantly higher Kt/V than the men (2.16 +/- 0.43 v 1.93 +/- 0.59; P < 0.01), Repeat peritoneal equilibration test was done after a mean duration of 10.5 +/- 4.9 months in 33 patients. Although the mean exchange volume (8.37 +/- 0.83 v 9.32 +/- 1.72; P = 0.003) increased significantly, weekly creatinine clearance (62.3 +/- 25.6 L/1.73 m(2) to 63.1 +/- 18.3 L/1.73 m(2); P < 0.05) and other kinetic parameters did not change markedly with duration. There was a tendency for the patients to move from the extreme transport groups to the average category with duration, (C) 1997 by the National Kidney Foundation, Inc.