A controlled study was undertaken to delineate any toxic effects of sorbitol in peritoneal dialysate. Nine patients were dialyzed with sorbitol solutions. Two who received the most total intraperitoneal sorbitol developed mental confusion and weight gain or edema in association with higher levels of serum and CSF sorbitol and an increase of serum and CSF osmolarity. Measures of hematologic, hepatic, cardiac, pulmonary and neurologic function did not reveal a specific toxic effect of sorbitol to these organ systems. Hyperglycemia occurred with both dextrose and sorbitol dialysate. No advantages of sorbitol dialysate as compared to dextrose dialysate were evident. While blood acid-base studies were consistent with respiratory alkalosis due to hyper-ventilation, CSF continued to show a compensated metabolic acidosis possibly due to an anion more slowly removed from CSF than blood during dialysis. CSF: serum distribution ratios for osmolarity, urea nitrogen, uric acid, creatinine and phosphate did not change during dialysis.