Over the last four years there has been an increase in the incidence of borderlineresistant Staphylococcus aureus isolated from bacteriological samples at the Ullevål University Hospital, Department of Medical Microbiology. Several severe infections caused by these bacteria have been noticed in the Department of Infectious Diseases at Ullevål University Hospital. From December 1994 to April 1997, 24 patients suffering from this type of S. aureus infection were examined with regard to clinical and microbiological outcome. 15 of the patients had hospital-acquired infections, and all except one had acquired the infection in Norway. 13 of the patients had at least one predisposing factor, 50% had received antibiotics (mainly cefalosporins) beforehand. Three of the 24 patients died from the infection. We discuss etiology, identification of groups at risk and management of the infection.