T-1982 (cefbuperazone), a new 7 alpha-methoxycephem antibiotic, was fundamentally and clinically studied, and the following results were obtained. The antibacterial activities of T-1982 against clinical isolates of S. aureus, E. coli, K. pneumoniae, S. marcescens, P. mirabilis and P. aeruginosa were determined in comparison with those of CER, CEZ, CMZ and CTT. Against S. aureus, CER and CEZ exhibited excellent activity, whereas T-1982 was less active with the peak MIC of 12.5 micrograms/ml even with the inoculum size of 10(6) cells/ml. The activity of T-1982 was equal to that of CTT and by far superior to that of CER, CEZ and CMZ against E. coli, K. pneumoniae and P. mirabilis, the peak MICs with the inoculum size of 10(6) cells/ml being less than or equal to 0.1-0.2 microgram/ml, less than or equal to 0.1-0.2 microgram/ml and 0.2-0.39 microgram/ml, respectively. Against S. marcescens, T-1982 was superior to CMZ and CTT and 48% of the strains were inhibited by 3.13 micrograms/ml or less, whereas all the strains were resistant to CER and CEZ. The MIC of T-1982 against most strains of P. aeruginosa was more than 100 micrograms/ml. 10 mg/kg or 20 mg/kg of T-1982 was administered by one shot intravenous injection or 1 hour drip infusion to 23 pediatric patients to measure serum levels and urinary recovery. At 30 minutes after one shot injection of 10 mg/kg and 20 mg/kg, the highest serum levels of 22.0-38.8 micrograms/ml and 52.4-80 micrograms/ml were observed, the half-lives being 1.32 hours and 1.76 hours. When given by 1 hour drip infusion, the serum levels attained the peaks of 29.2-42.6 micrograms/ml and 49.0-75.6 micrograms/ml at the end of infusion, the half-lives being 1.24 hours and 1.19 hours. The urinary recovery rates within 6 hours were 74.2-92.5% and 50.2-66.5% by one shot injection and 63.4-84.2% and 53.9-79.0% by drip infusion. T-1982 was administered at a dose of 50 mg/kg by 30 minutes drip infusion to a child with purulent meningitis. The levels of T-1982 in the cerebrospinal fluid at 1 hour after administration were 4.8-6.7 micrograms/ml with the CSF/serum ratios of 4.4-8.4%. A total of 36 pediatric patients (21 cases of respiratory tract infection, 9 cases of urinary tract infection and each 1 case of purulent cervical lymphadenitis, scarlet fever, purulent meningitis, acute colitis, peritonitis and sinusitis) was treated with 40-80 mg/kg/day of T-1982 (252.6 mg/kg/day in purulent meningitis). The response was excellent in 27 patients and good in 7 patients, the efficacy rate being 94.4%. Diarrhea or eruption were observed in each 1 case. No abnormal laboratory findings were noted in any cases.