During the period 1976-1980 Staphylococcus aureus was found in 265 blood cultures from 13 clinics for adult patients at Lund Hospital. Criteria of septicaemia were fulfilled in 169 patients, 65 had transient bacteremia and 31 cases were not evaluable. Concerning bacteriological data no Staphylococcus phage type dominated and strains resistant to antibiotics other than penicillin were very few. On the average 74% of the strains produced penicillinase with a successive increase during the study period. The incidence of septicaemia was highest in the decade 61-70 years of age. In patients with hospital-acquired septicaemia (n = 99) the main portals of entry for infection were vascular and/or surgical wounds (confirmed by phage typing in 93%). Patients with community-acquired septicaemia (n = 70) often had skin lesions but only a few cultures were taken. Only 4 patients were drug addicts. In 28 patients with no obvious portal of entry 14 nasal cultures were performed. Eight of ten positive cultures showed the same strain in nares as in blood at onset of sepsis. Secondary infectious foci were most frequent (26%) in patients with community-acquired infection. Endocarditis were found in 19 patients, 11 were diagnosed at autopsy. In staphylococcal endocarditis the mortality was 68% compared to 10% in septicaemia without endocarditis. In septic shock, compromised hosts and in connection with chronic diseases the mortality rates were 39%, 26% and 29%, respectively.