The elderly constitute an increasing percentage of patients with infective endocarditis. The disease manifestations and outcomes in 53 episodes of endocarditis in patients over the age of 60 were reviewed and compared with 55 episodes of endocarditis in patients less than 40 years of age and 46 episodes of endocarditis in patients aged 40 to 60. The percentage of cases caused by staphylococci and streptococci were roughly equal in all groups. Enterococci, Streptococcus bovis, and coagulase-negative staphylococci were more common in the elderly. In the elderly, invasive vascular procedures were the most common source of infection. Endocarditis acquired nosocomially accounted for 23 percent of all episodes in older patients. The elderly reported fewer symptoms and showed a diminished febrile response. Errors in diagnosis were noted in 68 percent of elderly patients, and a delay in initiating appropriate therapy was more common in this age group. The mortality rate was significantly higher in the elderly (45.3 percent) than in the middle-aged (32.6 percent) and young (9.1 percent). Endocarditis in elderly patients is often nosocomially acquired, is difficult to diagnose, and is associated with a higher mortality than noted in younger patients.