OBJECTIVE To report our first clinical experience with a new continuous ambulatory peritoneal dialysis (CAPD) fluid (PD-Bio), which is nearly devoid of glucose degradation products and has a higher pH (6.3) than conventional peritoneal dialysis (PD) solutions, and to discuss in general terms some acute and long-term effects of conventional acidic solutions containing glucose degradation products. METHODS 1) Pilot study on 4 patients investigated using a modified peritoneal equilibration test (PET) and cytobiology parameters. 2) Computer simulation study, assuming that conventional acidic solutions cause vasodilatation and recruitment of capillary surface area initially (during 0-60 minutes) in a PD dwell. METHODS Four stable CAPD patients were chosen in an open cross-over study. After a period of three months using conventional PD fluid, the patients were switched to three months on the new PD fluid. RESULTS Cancer antigen 125 increased significantly, and patients with discomfort/infusion pain during the control period improved during the period with the new fluid. No significant changes were observed in mass-transfer coefficients or drained volumes with the new solution. PH in the effluent dialysis was, however, higher for PD-Bio at all times during a two-hour dwell. In the computer simulation study, a less acidic solution caused an initially lower rate of glucose dissipation and improved ultrafiltration (UF) after a four-hour dwell, as compared to a conventional PD solution. CONCLUSIONS A new, differently produced, less toxic and less acidic PD fluid (PD-Bio) seems to be better tolerated than a conventional acidic solution with respect to discomfort/infusion pain. Theoretically, neutralized solutions should show slightly improved UF profiles over conventional acidic solutions, according to the computer simulation analysis. Furthermore, it is speculated that a neutral, less acidic, less toxic fluid would cause less interstitial-mesothelial alterations and less impairment of UF capacity than conventional solutions during long-term CAPD.