Objective. To compare an effectiveness of 0.9% saline solution and balanced isotonic Sterofundin solution for primary infusion therapy in early postoperative period in children. Material and methods. Open prospective randomized study included 43 children with ASA grade II—III after 1—3-hour surgery, blood loss less than 10% of the overall blood volume, no transfusions. Intraoperative infusion of a balanced Sterofundin solution at a dose of 12.8 (10.2; 15.6) ml/kg/hour was applied in all cases to maintain water-electrolyte balance. In the first group (n=23), early postoperative infusion therapy (3 hours after surgery) included 0.9% saline solution at a dose of 2.9 (2.3; 3.8) ml/kg/hour. In the second group (n=20), Sterofundin infusion at a dose of 3.1 (2.2; 3.5) ml/kg/hour was administered. Analysis of within-group and between-group differences included water-electrolyte and acid-base features, phase angle (integral parameter of cellular membranes), metabolic characteristics. Results. Significant between-group differences were obtained for serum K+ (p=0.01) at the 2nd stage, i.e. in 60 minutes after infusion onset. Other indicators were similar (p>0.05). pH significantly decreased by 1.2% in the 1st group and by 0.9% in the 2nd group compared to the values at admission to ICU. Total, extracellular and intracellular fluid volumes significantly increased in the 1st group by 3%, 3.4%, 2.7%, respectively. In the 2nd group, these values were 2.9%, 3.3% and 3.9%, respectively. Saline solution resulted more significant decrease (9%) in the phase angle, i.e. greater effect on the cellular membranes was observed compared to Sterofundin solution (4%). Both solutions did not significant influence basal metabolism. Conclusion. A 3-hour infusion of 0.9% saline solution (2.9 (2.3; 3.8) ml/kg/hour) and Sterofundin solution (3.1 (2.2; 3.5) ml/kg/hour) as initial solutions for early postoperative infusion therapy similarly influences water-electrolyte balance, serum acid-base state, cellular membranes and metabolism. Infusion of saline solution was associated with more significant reduction of pH towards acidosis and effect on cellular membranes.