The efficacy of the intravenous injection of aminophylline for treatment of acute exacerbations of bronchial asthma has been recognized since 60 years ago by many reports. It has been published on the "Asthma Prevention and Management Guidelines 1998, Japan" as one of important treatment for acute exacerbations of bronchial asthma. An intravenously Administered Theophylline (IAT) was newly developed in Japan in 2000. Different from aminophylline, the theophylline is not combined with ethylenediamine. We investigated efficacy and safety of IAT. In the present study, subjects were 16 asthmatic patients with mild acute exacerbations of bronchial asthma. They were administered IAT (200 mg theophylline with 200 ml saline) intravenously for two hours. After administration of the IAT, PEF and FEV1 were increased significantly. And severity of asthma, Borg scale, wheezing and breath sound were improved significantly. It should be emphasized that none of the patients treated in this study had any adverse symptom. The present study suggested that IAT is useful for patients with acute exacerbations of bronchial asthma.