A comparison was made between isocaloric amounts of 24% glucose and 24% Triofusin (composed of 120 g fructose, 60 g glucose and 60 g xylitol per liter) during the course of a 6-day, 3-phase crossover study of 15 patients undergoing total parenteral nutrition. The patients received a total of 0.5 g carbohydrate per kg per day. Plasma glucose as significantly higher during glucose infusion (7-22 mmol/l, median: 9 mmol/l,) than during Triofusin infusion (5-16 mmol/l, median: 6 mmol/l). A moderate to severe glucosuria was detected in three patients during infusion of 24% glucose, and this declined considerably during the Triofusin period. The total renal carbohydrate loss during the glucose period was 0-143 g, median: 6 g per day, and during the Triofusin period was 6-68 g, median: 10 g per day. The nitrogen balance and carbamide production rate were the same in the two infusion regimes. Changes in biochemical liver parameters were observed in most of the patients, but these could not be attributed to parenteral nutrition. None of the patients developed symptoms of metabolic acidosis. There was a slightly but significantly higher urinary excretion of oxalate in the Triofusin period (0.1-1.1 mmol per day, median: 0.5 mmol per day) than in the glucose period (0.1-1.0 mmol per day, median: 0.4 mmol per day). Most of the patients exhibited a slightly increased urinary excretion of urate, irrespective of the infusion regimen. Serum urate remained normal. It was concluded that Triofusin infused in the described dosage is a suitable calorie source for parenteral nutrition, but that it does not present a distinct advantage over the use of pure glucose solution. In patients suffering from reduced glucose tolerance, however, Triofusin represents a more easily manageable calorie course.