We encountered 6 patients with bronchial asthma complicated by mediastinal emphysema. Their average age was 21 years. All were atopic and had histories of asthma in childhood. In 5 of the 6, mediastinal emphysema developed when the patients had upper respiratory infections. In 3, the mediastinal emphysema worsened. After insertion of subcutaneous drains to decrease intramediastinal pressure, the conditions of those 3 patients improved remarkably. The conditions of the other 3 improved after medication only. During the period of this study, 1.24% of all patients treated at Hiroshima Asa Citizen's Hospital for exacerbations of asthma had mediastinal emphysema.