Acute normovolemic haemodilution was performed in 34 children (4-6 years old, weight: 16-68 kg) in whom major blood loss was expected during operation. Anaesthesia was induced with thiopentone, and then maintained with N2O/O2, fentanyl and pipecuronium. IPPV was used to maintain normocapnia. Heart rate, blood pressure, central venous pressure and core body temperature were monitored during haemodilution and throughout the surgery. A predetermined volume of blood to reduce hematocrit value to 30% was withdrawn in standard collection bags. In one child from Jehovah's Witness family hematocrit following haemodilution was only 20%. Every 1 ml of withdrawn blood was replaced with 1 ml of Haemaccel (Boehring, 32 children) or with 3 ml of isotonic crystalloid solution (PWE Polfa, 2 children). The blood lost during surgery was replaced with crystalloid solution and Haemaccel. Normovolemic loss of blood to haematocrit value of 20-24% was permitted. Retransfusion of collected blood was started when major bleeding was over, or when hematocrit decreased below 20-24%. Only 8 children needed homologous blood transfusion. Heart rate decreased significantly during haemodilution, while blood pressure remained stable. Low initial haematocrit and coagulopathy due to dilution of the plasma clotting factors were the limiting factors of the method. Partial thromboplastin time and plasma fibrinogen should be monitored throughout surgery, because the occurrence of coagulopathy promptly allows to initiate retransfusion of autologous blood.