We investigated clinical and bacteriological effects of cefetamet pivoxil (CEMT-PI) on community-acquired respiratory tract infection and obtained the following results: This method of investigation was almost the same to those adopted in 1994 and 1996. 1. 512 cases of respiratory tract infection were treated with CEMT-PI under the same protocol at a total of 53 institutions in Tokyo, Kanagawa, Saitama, Chiba and Yamanashi prefectures from January, 1, 1998 over March, 31, 1998. Outpatients accounted for 99.7% of all subjects. Diagnoses given to these patients included pharyngolaryngitis (51.4%), tonsillitis (37.7%), and acute bronchitis (10.1%). 2. For the bacteriological study, a manual detailing the method of collecting specimens, storage and transport was distributed to the above-mentioned institutions. The isolation and identification of suspected causative bacteria, determination of minimum inhibitory concentrations (MICs), and investigation of beta-lactamase production were conducted all together at Section of Studies, Tokyo Clinical Research Center. Suspected causative bacteria were detected in 144 (37.2%) out of 387 cases that were the analytical subjects of the clinical efficacy. The major bacteria identified were 32 strains of Streptococcus pyogenes and 19 strains of Haemophilus influenzae. The clinical efficacy (the ratio of improvement) of CEMT by suspected causative bacterium was 84.4% against CEMT-indicated organisms and 81.2% against CEMT-non-indicated organisms. 3. We investigated clinical efficacy rates (the ratio of "markedly improved" + "improved") by disease. The improvement rate was 78.4% in pharyngolaryngitis, 87.0% in tonsillitis, and 79.5% in acute bronchitis. The clinical efficacy rate was an average of 81.9% in all CEMT-PI indicated diseases.