Flomoxef (FMOX, 6315-S), a new antibacterial drug, was administered to 9 cases with respiratory tract infections for a duration of 8 approximately 16 days at a daily dose of 2 g. Diagnosis of these patients were bronchopneumonia 5 cases, chronic bronchitis 3 cases and acute bronchitis 1 case. From transtracheal aspiration several organisms were isolated; Haemophilus influenzae was isolated in 3 cases, Streptococcus pneumoniae in 3 cases, H. influenzae plus Branhamella catarrhalis in 1 case, Streptococcus dysgalactiae plus Neisseria meningitidis in 1 case and Corynebacterium pseudodiphtheriticum in 1 case. The clinical efficacy was good in all 9 cases, the efficacy rate was 100%. All the bacteria were eliminated. Side effects were not observed. From these results, it appears that FMOX is a valuable drug in the treatment of respiratory tract infections.