Cefmenoxime (CMX) has been administered under parenteral injection to 39 neonates delivered at term, nearly always by monotherapy in an average dosage of 86.8 mg/kg/day. CMX has been used 31 times in first line therapy and 8 times after failure of association Ampicillin-Gentamicin. 25 strains have been identified: 16 E. coli (9 Ampicillin resistant), 7 P. mirabilis (1 Ampicillin resistant), 1 K. oxytoca and 1 Streptococcus B. The neonates group with septicaemia (1 with arthritis) has been cured without after-effects as urinary tract infections and systemic infections. 2 respiratory tract infections have been improved, the others have been cured. Bacterial samples have always been sterilized within 2 days. Local tolerance (IV or/and IM injection) has been very good. No clinical or biological abnormality has been imputed to treatment. Cefmenoxime appears very effective on enterobacteriaceae (MIC range 0.05-0.5 mg/l) and can be used in newborn infections.