Cefadroxil was administered orally at a daily dose of 30-40 mg/kg to 8 cases of the infection of upper respiratory tract mainly due to beta-hemolytic Streptococcus, and efficacy was obtained in 7 cases, this rate being considered to be satisfactory, though the cases were too few to reach a conclusion. As to pathogens of bacterial infection of upper respiratory tract, beta-hemolytic Streptococcus and Staphylococcus aureus were encountered especially frequently, and in view of antibacterial activity against these 2 bacteria, our results could be approved. Further investigations should be performed carefully, however, to determine if cefadroxil may be a drug of first choice in the treatment of severe bacterial pneumonia and pyothorax. No side effects were observed throughout our treatment, though digestive tract disorders, especially diarrhea, are most frequent in literatures. As to pharmacokinetical characteristic of cefadroxil, almost the same results were obtained to other reports, though our data are insufficient as our experience was limited in only 1 case. Serum levels were determined after 35.7 mg/kg of cefadroxil were administered once orally, and a peak of about 38 mcg/ml appeared 2 hours later, and a high level of about 30 mcg/ml was maintained at 5 hours, though an oral dose was high. Efficacy for large area of bacterial infections may be expected from these serum levels. From urine collected simultaneously, about 74% of cefadroxil was recovered within more than 4 hours. This showed that cefadroxil was well absorbed from digestive tract, and a major part was excreted rapidly through kidney. From the results of our experiment, characteristics of cefadroxil may be summarized as follows. Cefadroxil is absorbed well after oral administration, antibacterial action is fully expected from serum level, a major part is excreted through kidney, and clearance is good. Cefadroxil will be recommended especially for bacterial infections of upper respiratory tract due to beta-hemolytic Streptococcus and Staphylococcus aureus.