As compared to the characterization of IE in the 1970s and early 1980s, it appears that IE in the 1990s is more likely to present acutely and in association with fewer classic stigmata and is more likely to be caused by S. aureus. Whether this represents a true clinical and microbiological shift in disease spectrum or is the result of reporting bias is unclear at this time. The ability to clinically designate a case definitely as IE has been improved with utilization of new diagnostic criteria that incorporate findings from two-dimensional echocardiography in the classification schema. These new criteria have been validated in selected patient populations but remain to be validated in other patient groups at risk for IE (e.g., prosthetic-valve recipients). Two-dimensional echocardiography is the noninvasive technique of choice for defining vegetative IE. TEE is significantly more sensitive in identifying valvular vegetations than is TTE, and TEE also is the method of choice for delineating periannular complications of IE. The role of Doppler flow assessment of valvular regurgitation in IE remains to be clarified. Short-course (2-week) regimens of beta-lactam agents plus aminoglycosides appear to be highly effective for the treatment of right-sided IE due to S. aureus. The use of vancomycin for treatment of S. aureus IE remains problematic because of reports of slow response and suboptimal treatment outcomes.