At present dialysis solutions with different glucose concentrations are used for the peritoneal equilibration test (PET) and Fast-PET in peritoneal dialysis (PD). We compared the results of two Fast-PETs, using 1.36 and 3.86% solutions sequentially in 30 patients on PD treatment, to obtain information on peritoneal transport (D/P-4 h) and ultrafiltration rates. Creatinine, phosphorus and urea D/P-4 h in the two Fast-PETs were not statistically different, unlike those for potassium, beta 2-microglobulin and glucose. The creatinine and phosphorus D/P-4 h values in particular proved to be uninfluenced by the different dialysis solutions. The lack of correlation between the two Fast-PET ultrafiltration values confirmed the difficulty in interpreting this parameter, above all in the case of non-homologous Fast-PETs. We obtained useful indications for comparing different Fast-PET results, but were unable to reach a decisive conclusion regarding the best of the two dialysis solutions for this test.