The clinical efficacy and the safety of sultamicillin (SBTPC) fine granules, which is a semisynthetic beta-lactam antibiotic for oral use with ester linked ampicillin (ABPC) and sulbactam (SBT), a beta-lactamase inhibitor, in a ratio of 1:1, were evaluated in 31 patients with ages from 6 months old to 10 years and 4 months old with various bacterial infections. The results obtained are summarized as follows. 1. In a pharmacokinetic study with a dose level of 10 mg/kg SBTPC, serum levels reached a peak in 1 hour after oral administration, with peak levels of 3.94 micrograms/ml for ABPC and 4.08 micrograms/ml for SBT. Half-lives of ABPC and SBT were 64.8 minutes and 63.6 minutes, respectively. The urinary excretion of ABPC over 6 hours was 66.2% and that of SBT was 60.4%. 2. SBTPC fine granules were administered orally to 1 patient with bronchitis, 9 patients with bronchopneumonia, 7 patients with tonsillitis, 4 patients with scarlet fever, 1 patient each with pharyngitis, otitis media, purulent parotitis, and urinary tract infection and 6 patients with skin and soft tissue infections at daily dosage levels of 26.1-31.6 mg/kg divided into 3 or 4. Clinical evaluations of these 31 patients were as follows, excellent: 20 patients, good: 10 patients, poor: 1 patient. The efficacy rate was 96.8%. 3. Diarrhea was observed in a patient with otitis media on the fifth day of SBTPC administration. No other clinical adverse reaction was observed in any of the remaining 30 patients. No abnormal laboratory data was found in any of 23 patients who were subjected to laboratory examinations for safety.(ABSTRACT TRUNCATED AT 250 WORDS)