Hypoxaemia is a common problem causing child deaths in developing countries, but the cost-effective ways to address hypoxaemia are ignored by current global strategies. Improving oxygen supplies and the detection of hypoxaemia has been shown to reduce death rates from childhood pneumonia by up to 35%, and to be cheaper per life saved than other effective initiatives such as conjugate pneumococcal vaccines. Oxygen concentrators provide the cheapest and most consistent source of oxygen in health facilities where power supplies are reliable. To implement and sustain oxygen concentrators requires strengthening of health systems, with clinicians, teachers, administrators and technicians working together. Programmes built around the use of pulse oximetry and oxygen concentrators are an entry point for improving quality of care, and are a unique example of successful integration of appropriate technology into clinical care. This paper is a practical and up-to-date guide for all involved in purchasing, using and maintaining oxygen concentrators in developing countries.