Ceftizoxime (CZX) was used for 33 patients with respiratory tract infections; 22 patients with pneumonia, 3 patients with pulmonary abscess, 4 patients with diffuse panbronchiolitis and 4 patients with acute exacerbation of bronchiectasia. Clinical effects of CZX were evaluated in 33 patients; excellent in 16 and good in 14 patients. The efficacy rate was 91%. Bacteriological effects of CZX were prominent in 7 patients infected with S. pneumoniae, H. influenzae, K. pneumoniae and Citrobacter, but not in a patient infected with P. aeruginosa. The elimination rate was 92% (12/13). As the side effects, exanthema in 1 patient and gastrointestinal symptoms (nausea and vomiting) in 1 patient were observed. However, they improved without any treatment by cessation of CZX use. Abnormal laboratory findings were observed in 2 patients with elevated GOT and/or GPT. They normalized after cessation of drug. The usefulness of CZX was 82% (27/33). Therefore, CZX is a very useful drug and its effects are promising in clinical management of respiratory tract infections.