Cefuzonam (L-105, CZON) was studied in pediatric infections. A summary of the results it as follows: For recently isolated Staphylococcus aureus strains, Peak MICs of CZON were distributed between 0.39 and 0.78 micrograms/ml showing a greater susceptibility of S. aureus to CZON than to cefoperazone (CPZ), latamoxef (LMOX), and cefmenoxime (CMX). Peak MICs of CZON for Escherichia coli were 0.10-0.20 micrograms/ml, similar to those of CPZ, LMOX, and CMX. Ampicillin (ABPC)-resistant strains were also susceptible to CZON. MICs for Salmonella were similar to those for E. coli. Peak MICs of CZON for Vibrio parahaemolyticus were 0.20-0.39 micrograms/ml. The susceptibility of the bacteria to CZON was far greater than to ABPC, and was similar to CPZ, LMOX, and CMX. With 20 mg/kg drip infusion, serum concentrations reached their peaks at the end of administration with values of 20.6-68.7 micrograms/ml, which decreased to 0.43-1.70 micrograms/ml after 2 hours. Half-lives of CZON in serum were 0.68-1.2 hours. With 50 mg/kg drip infusion, serum concentrations reached their peaks at the end of administration with levels of 69.0-82.0 micrograms/ml, and at after 2 hours 1.85-3.45 micrograms/ml. Thus, an apparent dose response was observed. Half-lives of CZON in serum were 0.63-0.99 hours. Urinary recovery rates in 6 hours were 39.9-80.5%. A total of 44 cases of 10 different types of acute pediatric infections was treated by CZON intravenous drip infusion as the main therapeutic procedure. The efficacy rate was 93.2%, and the compound was effective on purulent infections, acute urinary tract infection, etc. with pathogens such as ABPC-resistant S. aureus, E. coli, and Enterococcus faecalis. Dosage levels per day were 50 to 80 mg/kg in most cases. In infections with S. aureus (8 strains), Streptococcus pneumoniae (3 strains), E. faecalis (1 strain), Haemophilus parahaemolyticus (1 strain), Haemophilus parainfluenzae (2 strains), Haemophilus influenzae (11 strains), Bordetella pertussis (1 strain), E. coli (3 strains), a total of 30 strains, bacterial elimination was noted with an exception of 1 strain of S. aureus. The compound was used for 4 to 15 days, but side effects observed clinically were only 1 case of diarrhea and 1 case of thrombocytosis.