Biapenem (L-627) was evaluated for its safety and efficacy in 27 children with various bacterial infections. L-627 was effective in cases with osteomyelitis due to Staphylococcus aureus, pneumonia and purulent meningitis due to penicillin-resistant Streptococcus pneumoniae, and urinary tract infections due to Enterococcus faecalis, Escherichia coli, or Pseudomonas aeruginosa. However, L-627 failed to produce good responses in 2 of 7 cases of Haemophilus influenzae infections. Pharmacokinetic parameters of 30-minutes infusion of 12 mg/kg were as follows: Cmax 29-46 micrograms/ml, T 1/2 0.68-0.94 hr. Adverse reactions were minimal. These data suggest that L-627 is safe in children, and is valuable especially for treatment of infections in immunocompromised hosts and infections due to multiply resistant bacteria.