The risk of nosocomial infection due to Staphylococcus aureus in fullterm newborns is higher under hospital conditions where there are overcrowded nurseries and inadequate infection control techniques. We report on an outbreak of skin infection in a Maternity Nursery (May 21, 2000) and the measures undertaken to bring the epidemic under control. These measures included: separating neonates already present in the nursery on August 23, 2000 from ones newly arriving by creating two different cohorts, one of neonates born before this date and one of neonates born later; restricting healthcare workers caring for S. aureus- infected infants from working with non-infected infants; disallowing carrier healthcare workers from caring for patients; introducing contact and droplet precautions (including the routine use of gowns, gloves, and mask); ensuring appropriate disinfection of potential sources of contamination. A representative number of isolates were typed by genomic DNA restriction length polymorphism analysis by means of pulsed-field gel electrophoresis (PFGE). Among the 227 cases of skin lesions, microbiological laboratory analyses confirmed that 175 were staphylococcal infections. The outbreak showed a gradual reduction in magnitude when the overcrowding of the Nursery was reduced by separating the newborns into the two different Nurseries (two cohorts). The genotyping of the strains by PFGE confirmed the nurse-to-newborn transmission of S. aureus. The measures adopted for controlling the S. aureus outbreak can, in retrospect, be assessed to have been very effective.