Perinatally acquired bacterial neonatal sepsis is a low-incidence,high-risk disease. Although incidence of the most common etiology,group B Streptococcus, has been reduced by prophylactic strategies,neonatal sepsis has not been eradicated, and vigilance must remain high. Accurate diagnosis is difficult: signs and symptoms are hard to distinguish from other causes of neonatal distress, and definitive diagnostic tests are not available. The clinician must make a judgment call, considering the perinatal history, the constellation of signs and symptoms, and the results of existing diagnostic tests,before neonatal sepsis can diagnosed or excluded. With diagnosis,knowledge of the specific disease states and clinical algorithms for management aid in formulating a plan of treatment with antimicrobial agents and supportive care.