The clinical picture of S aureus endocarditis remains relatively uncharacteristic, and a number of nonspecific symptoms of infection (eg, chills, nausea, vomiting, myalgia, and arthralgia) were each reported only infrequently. It has obvious implications to distinguish clinically uncomplicated S aureus bacteremia from endocarditis. The absence of either a cardiac murmur or signs of congestive heart failure by no means excludes the presence of endocarditis; therefore, a major question that needs to be answered is, "What clinical factors should arouse suspicion that endocarditis is present in a patient with S aureus bacteremia?" This question was addressed more than 20 years ago by Nolan and Beaty.18 In a retrospective study of 105 cases of S aureus bacteremia, they found that 24 of 26 cases of endocarditis were characterized by the following triad: (1) community-acquired S aureus bacteremia that (2) arose from an inapparent primary focus and (3) was associated with metastatic sequelae. In contrast, only 2 cases of endocarditis were acquired nosocomially from an obvious primary focus with no metastatic sequelae. From the few studies conducted since then with the purpose of verifying the utility of these criteria, it appears that the Nolan and Beaty parameters have insufficient predictive value in a population of non–drug addicts with S aureus bacteremia to be used as the only tools for diagnosing endocarditis.19 The insufficiency of these criteria agrees with the results of our study. First, approximately one third of the 8500 cases of S aureus bacteremia reported during the study period were community acquired. This means that even if the frequency of endocarditis is higher when community-acquired infection is compared with nosocomial infection, the difference is only a factor of 4. Second, although found less frequently in community-acquired cases, a primary focus was still identified in 40% of these patients. Third, an obvious primary focus was identified in 71% of the nosocomially acquired cases of endocarditis, and metastatic involvement of the central nervous system was observed with the same frequency as in the community-acquired cases.12 In this context, however, it must be mentioned that there was no follow-up beyond the hospital stay for the patients. This lack of follow-up represents a limitation to our study, as serious complications due to endocarditis, including metastatic sequelae, can occur several months after treatment has ended. Of particular interest, however, is the fact that an intravascular catheter was identified as a primary focus in 25% of the patients with nosocomial infection. Thus, even though it is true that most cases of S aureus bacteremia acquired in the hospital and relating to indwelling intravascular devices rarely represent or eventuate in endocarditis,19- 20 these cases nevertheless represent one tenth of the patients in the present study. A more frequent identification of a primary focus did indeed characterize the patients who were not diagnosed clinically. Thus, it is extremely important to emphasize that a primary focus of the infection by no means excludes the coexistence of endocarditis. In conclusion, in many cases, it is impossible to differentiate uncomplicated S aureus bacteremia from endocarditis clinically, and it is imperative to increase diagnostic efficiency by using echocardiography. The question is, "Which patients should undergo screening by transthoracic echocardiography?" Based on our results, it is difficult to make firm recommendations, but it does not seem justified to restrict such screening to patients with community-acquired S aureus bacteremia.