OBJECTIVE: To review the current medical literature on neonatal nosocomial infections, emphasizing aspects of neonatal colonization, immune system and infection mechanisms, modes of transmission, epidemiology, surveillance and prevention of these infections, in addition to assessing peculiarities about etiologic agents and prophylactic recommendations. SOURCES: Electronic search in the Medline and LILACS databases, with selection of the most relevant articles published within the last ten years. SUMMARY OF THE FINDINGS: The several peculiarities that cause greater susceptibility to infection in newborns, and the survival of preterm infants due to the invasive procedures and treatment with broad spectrum antibiotics at intensive care units are responsible for prevalence rates of neonatal nosocomial infections between 9.3 and 25.6%. Neonatal nosocomial infections affect at least 50% of newborns who weigh less than 1500 g, which ends up increasing mortality rates. Full-term newborns frequently have skin and soft tissue lesions caused by gram-positive organisms. In neonatal intensive care units, sepsis and pneumonia are frequently diagnosed (especially those caused by S. aureus, S. epidermidis, E. coli, K. pneumoniae, and E. cloacae). An increasing frequency of resistance to several antimicrobial drugs has been observed. A nosocomial infection surveillance program tailored to the characteristics of the neonatal unit allows the identification of infection outbreaks, the rational use of antibiotics and the application of preventive measures. CONCLUSIONS: Neonatal nosocomial infections are a relevant problem. Their control can only be achieved if adequate measures concerning pregnant women, hospital environment, nursing staff, and newborns are adopted. Although new prophylactic measures are being proposed for preterm infants, they are costly and do not preclude continued epidemiological surveillance and control in neonatal units.