This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: Primary objectives To determine the effectiveness of oxygen therapy in the treatment of severe LRTIs in children. To determine the effectiveness of the different oxygen delivery methods in the treatment of severe acute LRTIs in children. Secondary objectives To describe the indications for oxygen therapy in children with LRTIs. To determine the frequency of treatment failure or clinical deterioration in both groups of children (with oxygen therapy versus without oxygen therapy). To describe the factors (type of underlying disease, severity of hypoxemia at presentation etc) influencing the duration of hypoxaemia in each group (each oxygen delivery method). To describe the side effects of each method. To describe the clinical criteria for ending oxygen therapy. To determine the indications for continuing oxygen therapy after discharge. To estimate costs associated with each method of oxygen delivery.