Hypoxaemia is a common complication of stroke, and an association between adverse outcomes and hypoxaemia has been reported. However, it remains unclear whether hypoxaemia is the cause or just a sign of poor prognosis. While clinical guidelines unanimously recommend treatment of hypoxaemia after stroke, the guidance does not specify at what level of hypoxaemia treatment should be started. Recent evidence from a Swedish study suggests that overtreatment can also have detrimental effects on outcome. The aim of this review is to explore issues relating to hypoxaemia after stroke.