Fundamental and clinical studies of flomoxef (FMOX, 6315-S) were conducted and the obtained results are summarized as follows. For the pharmacokinetic investigation, FMOX at 10 or 20 mg/kg was administered by intravenous drip infusion over 30 minutes. In the 10 mg/kg group, the maximum blood concentration was reached just after completion of the drip infusion with the mean concentration of 30.3 +/- 4.5 micrograms/ml, and the mean half-life was 0.734 +/- 0.196 hour. The 6-hour urinary excretion rate was 72.3%. In the 20 mg/kg group, which also showed the peak concentration immediately after completion of the drip infusion, the mean peak blood concentration was 54.3 +/- 9.7 micrograms/ml and the mean half-life was 0.628 +/- 0.185 hour. The 6-hour urinary excretion rate was 69.3%. The urinary recovery tended to be lower in children than in adults. Between 10 mg/kg and 20 mg/kg, a definite correlation was observed between dose levels and blood concentrations. In the clinical investigation conducted with a total of 30 patients (22 with respiratory tract infection, 3 with lymphadenitis, 2 each with urinary tract infection and cellulitis, and 1 with acute osteomyelitis), FMOX was found to be excellent in 14 cases, good in 9, fair in 1, poor in 1, and not evaluable in 5. The efficacy rate was, therefore, 92.0%. In the bacteriological evaluation, 8 out of 12 clinically isolated strains were eradicated, 2 unchanged and 2 unknown. The elimination rate was 80.0%. Regarding side effects, no abnormal clinical symptoms were observed. As abnormal laboratory values, eosinophilia, prolongation of APTT, increased platelet count, and a slight elevation of GOT were observed.