Six patients established on continuous ambulatory peritoneal dialysis entered a trial of treatment with dialysis fluid containing glycerol instead of glucose as the osmotic agent in an attempt to decrease the energy load. They were observed for a further 6 months after reconversion to glucose-based dialysis. During the 6 month control period fluid balance was achieved mainly with a solution containing 76 mmol of glucose/1. Fluid balance was maintained during the 6 month period of treatment with glycerol only by the increased use of solutions containing a high concentration of glycerol (152 mmol/l and 272 mmol/l). Thus the energy value of the absorbed osmotic agent did not differ at a mean of 1607 kJ (384 kcal)/day using glycerol and 1669 kJ (399 kcal)/day using glucose as the osmotic agent. In five subjects, fasting and peak blood glycerol levels did not change over the 6 months, but one subject, who accumulated glycerol, developed symptoms of hyperosmolality after 2 months and glycerol therapy was discontinued. In a further subject glycerol-based dialysis was terminated at 3 months when increasing angina was reported. Mean fasting plasma triglyceride concentrations were 50% higher during the 6 months on glycerol (3.12 +/- 1.12 mmol/l) than on glucose (2.19 +/- 0.97 mmol/l) (P less than 0.05). There was a small rise in very low density lipoprotein-cholesterol concentrations with glycerol dialysis but total cholesterol levels were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)