Thirty-eight children completed therapy with moxalactam for a variety of non-CNS infections. Haemophilus influenzae type b (seven ampicillin-resistant strains) was the etiologic agent for 32 children. Doses of moxalactam ranged from 113 to 200 mg/kg/d in three or four divided doses administered parenterally. All children with infections due to H influenzae type b had excellent responses to moxalactam therapy. Children treated for infections due to other agents also responded satisfactorily to moxalactam therapy. Moxalactam concentrations in joint and pleural fluids greatly exceeded the minimal bactericidal concentrations of moxalactam for H influenzae type b. Adverse reactions included neutropenia, eosinophilia, thrombocytosis, and transient elevation of transaminase levels. Moxalactam administered parenterally, at a dose of 113 to 150 mg/kg/d in three or four divided doses is effective therapy for serious infections in children due to H influenzae type b and selected other organisms.