To demonstrate clinical value of clavulanic acid/amoxicillin (CVA/AMPC) 1:14 combination dry syrup for acute bacterial rhinosinusitis (ABRS), the efficacy and safety were evaluated in a multicenter, open-label, uncontrolled study in 27 children with ABRS. The proportion of subjects who were 'cured' at the test of cure as the primary endpoint was 88.5%. In subjects with a major pathogenic bacteria at baseline (i.e., Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis) bacterial eradication was achieved in ≥ 80% of the subjects with the exception of β-lactamase non-producing ampicillin resistant H. influenzae: BLNAR and β-lactamase producing ampicillin resistant H. influenzae: BLPAR (β-lactamase producing amoxicillin/clavulanic acid resistant H. influenzae: BLPACR). The MIC of CVA/AMPC (1:14) was not higher than 4 μg/mL for all pathogens except one strain each of BLNAR and BLPAR (BLPACR). Drug-related adverse events were reported in 19% of patients (5/27 patients). All of the reported drug-related adverse events were classified as gastrointestinal disorders that have been commonly reported with antibacterial drugs. These results indicate that CVA/AMPC (1:14) was clinically useful for the treatment of ABRS and is also suggested that was effective especially for the treatment of ABRS in children caused by beta-lactamase-producing bacteria including M. catarrhalis.