Thirty-eight patients (10 cases and 28 controls) were included in a case-control study of Staphylococcus aureus bloodstream infection after cardiac surgery in 833 patients. All bacterial strains were found to be unique by pulsed-field gel electrophoresis. In multivariable risk-factor analysis, only valve prosthesis implantation was associated with bloodstream infection. The early and late case mortality rate was 0%.