Bacteriological, pharmacokinetic and clinical studies on cefditoren pivoxil (CDTR-PI, ME 1207) in granules, a new oral cephalosporin, were performed in the field of pediatrics. The results are summarized below. 1. Antibacterial activities: Antibacterial activities of CDTR were studied against Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae, Haemophilus parainfluenzae and Branhamella catarrhalis in comparison with those of cefteram (CFTM), cefixime (CFIX), cefaclor (CCL), cefpodoxime (CPDX) and cefotiam (CTM). MIC80's of CDTR against S. aureus, S. pneumoniae, S. pyogenes, H. influenzae, H. parainfluenzae and B. catarrhalis were 1.56, 0.39, < or = 0.025, < or = 0.025, 0.05 and 0.20 micrograms/ml, respectively. These results showed that CDTR has high antibacterial activities against these organisms. 2. Absorption and excretion: Serum concentrations and urinary recovery rates of CDTR-PI (administered in granules) were determined. Upon single oral doses of 3 mg/kg and 6 mg/kg, the peak serum concentrations were 0.5-2.45 micrograms/ml at 2 to 4 hours and 1.79-4.05 micrograms/ml at 1 to 4 hours, respectively, and T 1/2 was 1.07-9.67 hours and 0.99-3.00 hours, respectively. At 8 hours after dosing, serum concentrations were 0-0.87 micrograms/ml with a dose of 3 mg/kg and 0.27-0.73 micrograms/ml with 6 mg/kg. These values indicated that the drug has a dose-dependent pharmacokinetic behavior. Urinary recovery rates in the first 8 hours were 12.9-34.2% with a dose of 3 mg/kg and 11.8-26.9% with 6 mg/kg. 3. Clinical study: Clinical efficacies were examined in a total of 81 cases consisting of 20 cases of acute bronchitis, 13 of acute pneumonia, 21 of tonsillitis, 5 of pharyngitis, 7 of scarlet fever, 2 each of impetigo, otitis media and purulent cervical lymphadenitis, 1 of pertussis and 8 of UTI. The clinical efficacy rate was 97.5% (79/81), and bacteriological eradication rate was 100% (76/76). As for side effects, 2 cases of watery stools and 1 case of minor elevation of GPT were observed.