S 6472 granule preparation (sustained-release cefaclor) was orally administered to 15 patients with chronic respiratory tract infections (2 acutely exacerbated cases of chronic bronchitis, 13 cases of secondary infections consisting of 1 case of bronchial asthma, 2 cases of bronchial asthma/pulmonary emphysema, and 10 cases of bronchiectasis) at a daily dose of 750 mg divided into 2 doses administered after breakfast and dinner, for a duration of 14 days. The drug was ineffective in 3 of the 10 cases of bronchiectasis but was effective in the other 12 cases, with a rate of efficacy of 80%. There were no side effects of abnormal laboratory findings due to administration of this drug.