The aim of the study was to quantify the catabolism rate induced by simultaneous kidney-pancreas transplantation and to evaluate the impact of parenteral nutrition (PN) on recovery of graft function. Twenty-six diabetic uremic patients were studied. The average urea nitrogen production (UNP) was 5.2 +/- 1.7 g during the first 24 h after transplantation, while patients did not receive energy and nitrogen support. Energy (30 kcal.kg-1.day-1) and nitrogen (0.15 g.kg-1.day-1) intake started 24 h after surgery. In 14 patients, a mixed regimen was adopted (70% carbohydrates, 30% lipids), and 12 patients received only hypertonic glycidic solutions. The recovery of kidney function was immediate in all cases, with a prompt decrease in blood urea nitrogen and serum creatinine levels. C-peptide levels rose immediately after the revascularization of the pancreas graft and remained within the normal range during the PN period. No significant difference was observed in UNP or glucose tolerance between the mixed-regimen and glycidic groups. However, on average 6.6, and 1.5 hyperglycemic episodes occurred during the 1st wk of PN in the glycidic and mixed-regimen groups, respectively. The posttransplantation catabolism rate was similar to that induced by an elective major surgical procedure. Eucaloric PN did not affect the recovery of kidney and pancreas graft function. A mixed energy regimen seems to be most suitable for kidney-pancreas transplant patients because it prevents hyperglycemia which might be misdiagnosed as rejection.