Therapy for asthma is being prescribed more frequently. However, asthma mortality remains high in many countries. Fatal outcome is not always related to inadequate follow-up. In this article we report that children with mild to moderate symptoms may present a fatal attack. Many factors are responsible for such an outcome: asphyxia +3 due to ventilation/perfusion mismatch and/or bronchospasm, cardiac failure, cardiac arrhythmia, intrinsic positive expiratory pressure, or metabolic disturbances (hypokalemia, for example). Such problems can occur in predisposed patients: it has been shown that the chemosensitivity to hypoxia and the perception of dyspnoea are altered in certain patients with near-fatal asthma. It is very important to identify children at risk of severe asthma and to organize care so as to optimize the management of such children.