Long-lasting hypophosphatemia was previously found to diminish myocardial performance. The present study aimed to elucidate if postoperative glucose-induced hypophosphatemia is of importance for myocardial performance. Sixteen patients undergoing elective colonic or rectal surgery were given 100 g glucose intravenously (as 20% glucose solution) on the first and second postoperative days. The infusion rate was 0.3 g/kg/hour. On both days the glucose infusion caused significant fall in P-phosphate (0.94 to 0.67 and 0.71 to 0.47 mmol/l, respectively). No changes were seen in P-calcium, P-potassium or P-sodium. Measurements of stroke volume and frequency, central venous pressure and mean arterial pressure were made immediately before and after the glucose infusions. Stroke volume and cardiac output were unaffected during the infusions, and also from the first to the second postoperative day. As the preload (central venous pressure) and the afterload (arterial pressure) similarly were unchanged by the glucose infusion, glucose-induced hypophosphatemia following elective surgery was judged to lack importance for the myocardial performance.