All cases of neonatal bacteremia occurring at Neonatal Department of Pediatric Clinic, Catholic University of Rome, from January 1976 to December 1983 were examined retrospectively. Twenty-seven (30%) newborn infants with positive blood cultures for coagulase-negative staphylococcus were identified. Seven (25.9%) of the 27 infants were born at term, 4 AGA and 3 SGA; mean birth weight was 2,804 gm (range 2,280-3,670). All of these neonates had clinical evidence and laboratory signs of sepsis, and one had the cerebrospinal-fluid culture positive for coagulase-negative staphylococcus. In the remaining 20 infants (74.1%) the mean birth weight was 1,445 gm (range 810 - 2,400) and mean gestational age was 32 weeks (range 27 - 36). In 15 of the 20 preterm infants clinical signs of septicemia were associated with positive blood culture, and sixty percent of these had received an umbilical artery catheter. An half of coagulase-negative staphylococci isolated from our neonatal sepsis were DNAse-positive and/or phosphatase-positive and/or mannitol-positive. Two full-term infants, one with Down syndrome and one with cardiac malformation, died at 9 days and at 2 weeks of age, respectively. Three of 15 preterm infants with coagulas-negative staphylococcal septicemia died; deaths were among infants of very low birth weights and immature gestations who had severe respiratory syndrome. These data show that coagulase-negative staphylococcus can be important cause of septicemia in patients with compromised host defenses as newborn infants, and especially in the premature babies receiving invasive procedures.