An alternative oxygen delivery system for infants and children in the post-anaesthesia care unit. This randomized controlled trial compared the compliance of a blow-by oxygen method with the standard face mask by children recovering from anaesthesia. The rate at which a face mask was rejected when applied to infants and children in PACU was compared with that of a proposed "hose" method. The efficacy of the "hose" as a method of oxygen supplementation in children at low and high risk for developing postoperative hypoxaemia was also compared with the face mask. Using a Nellcor N-200 pulse oximeter, 66 infants and children (mean age 2.3 yr, range 2 mo-6 yr) were continuously monitored for 30 min upon arrival in the PACU. Patients were randomized to receive oxygen supplementation with either the face mask or the proposed "hose" method. The results showed a greater than 80 per cent rejection of the face mask in contrast to 100 per cent compliance with the "hose" method. The SaO2 measurements following 5, 15 and 30 min of O2 supplementation with the hose were all significantly higher than the SaO2 measurements obtained on room air upon arrival to the PACU. Patients with pre-existing cardiopulmonary disease had a 20 per cent incidence of arterial oxygen desaturation upon arrival to the PACU versus 2.1 per cent of patients with no pre-existing disease. It is concluded that the "hose" is associated with high patient compliance and is effective in the PACU in increasing the SaO2 in children at low or high risk of developing postoperative hypoxaemia. 