This study aimed to assess the efficiency and safety of military anti-shock trousers (MAST) in preventing venous air embolism in children undergoing neurosurgical procedures in the sitting position. It included 26 children, 7.7 ± 4-year-old and weighing 25.4 ± 10.5 kg. All had the same anaesthetic protocol including premedication with oral lorazepam, induction with thiopentone or propofol with fentanyl and vecuronium, and maintenance with isoflurane and a continuous infusion of fentanyl. In 10 patients, a retrograde central venous catheter was inserted for measurement of pressure in the superior bulb of the internal jugular vein. Haemodynamic measurements were carried out with the patient supine ; with the patient sitting, the MAST not being inflated ; 10 min after inflation of the MAST (40 mmHg in the limbs, 30 mmHg in the abdominal part) ; after starting 10 cmH 2 O positive end expiratory pressure ; and after fluid administration with 5 ml · kg −1 macromolecules (Plasmion®). The criterion for air embolism was a decrease in Petco 2 of more than 5 mmHg over more than 30 s, not preceeded by respiratory or cardiovascular impairment. Inflation of the MAST resulted in a dramatic rise in venous pressure, still reinforced by minor PEEP. Transmission of pressure from the right atrium to the dural sinus was linear, and seemed to be sufficient to prevent occurrence of detectable venous air emboli. No deleterious side-effects were noted. This method would therefore seem to be very efficient, preserving the advantages of the sitting position, and restricting its disadvantages. Unfortunately, the limited availability of different paédiatric sizes of MAST reduces the possible uses of this method.