The importance of the evaluation of dialytic adequacy is well known in peritoneal dialysis. It is necessary to be able to quantify and individualize the substitution treatment. In 15 patients we compared five quantitative approaches by using original software: Teehan's dialysis index (DI); Diaz-Buxo's liters/week (LW); Keshaviah's the quantity of dialysis prescribed (wKt/V); and Boen and Twardowski's weekly creatinine clearance (WC). All patients were treated by continuous ambulatory peritoneal dialysis (CAPD) according to the peritoneal equilibration test (PET). Peritoneal solute clearances for urea, creatinine, uric acid, and phosphorus were adequate, but there was disagreement between adequacy indexes. According to the DI, 40% of our patients were underdialyzed, 33% were adequate, and 27% received excessive dialytic dose, while according to LW and wKt/V, about 50% were adequate, 10% underdialyzed, and 40% received excessive doses. According to WC, 74% were overdialyzed and 26% were adequate. In two patients only (13%) all the indexes indicated underdialysis. We think that the DI is too severe an adequacy index, probably because residual renal clearances have a great weight in the formula, while WC may lead to an overestimate of the actual dose of therapy in patients with significant residual renal clearance. Prospective, randomized and clinical studies are needed to better assess the optimal index for individualization of targeted peritoneal dialysis prescription.