A study of 214 neonates (with 87 premature infants) reveals that C-reactive protein (CRP), orosomucoid and prealbumin are the most interesting proteins for the diagnosis of neonatal sepsis and for studying its follow-up. Orosomucoid is high in 85% of bacterial infections and CRP in 75%. Early type strep B infections give often false negative results. The evolution of CRP and of prealbumin corresponds to the effects of treatment and the evolution of orosomucoid is parallel to the healing of the patients. The ratio orosomucoid/prealbumin allows an earlier appreciation of the healing.