The tulobuterol transdermal therapeutic system (TTS) is the world's first commercially available transdermal preparation of tulobuterol, a beta-2 stimulant, that can maintain effective blood tulobuterol levels for 24 hours when applied once daily. In the present study, a total of 36 adult patients with mildly persistent (Step 2) or moderately persistent (Step 3) bronchial asthma 19 who were using inhalational steroids and 17 who were not used tulobuterol TTS for one year and underwent measurement of peak expiratory flow (PEF) once daily. Peripheral eosinophil count, serum eosinophil cationic protein (ECP) level and airway responsiveness (Dmin) were evaluated at 6 months and 1 year after the start of the study. PEF exhibited significant improvements at 6 months and 1 year in patients treated with or without inhalational steroids, while serum ECP was improved significantly only in the patients on inhalational steroids. Patients not using inhalational steroids exhibited no significant exacerbation of Dmin at either 6 months or 1 year: One-year treatment with tulobuterol TTS did not appear to cause tachyphylaxis. The significant improvements in Dmin at 6 months and 1 year in the patients using inhalational steroids suggested that inhalational steroids offer beneficial effects in controlling airway inflammation. Tulobuterol TTS is considered quite beneficial in improving quality of life (QOL) in patients with bronchial asthma because its incidence of adverse effects including palpitations and shivering is significantly lower than those of oral preparations, because of its remarkable improvement of pulmonary function and symptoms of airway obstruction without increasing airway responsiveness even after repeated use, and because it is simple to use and offers excellent clinical efficacy.