Clinical and bacteriological information of Staphylococcus aureus endocarditis was reviewed in 119 cases from all over Denmark. Overall mortality was 71%. Survival correlated with antistaphylococcal treatment, short duration from onset of infection to start of treatment, and long duration of treatment. In spite of relevant treatment, mortality was significantly lower in cases infected with penicillin-susceptible strains than when penicillin-resistant strains were isolated. There were no differences in the effect of various anti-staphylococcal treatment regimens; in particular, there were no differences in mortality with regard to beta-lactam antibiotics alone as compared to beta-lactam antibiotics in combination with aminoglycosides. However, embolic manifestations occurred more often after start of treatment with combination therapy than with beta-lactam antibiotics alone.