In an attempt to establish an appropriate management program for patients with active infective endocarditis, 30 patients treated during the past 20 years were studied retrospectively. Microorganisms were confirmed in 27 of the 30 patients (90%) (86.7% by culture and 3.3% at surgery). Among these 27 patients, viridans streptococci were confirmed in 23 (85.2%), aureus staphylococci in 2 (7.4%), epidermidis staphylococci in one (3.7%) and candida albicans in one (3.7%). Twenty of the 23 patients (87%) with viridans streptococcal endocarditis were treated medically with good success, but 2 patients (8.7%), who developed severe congestive heart failure (NYHA 3-4 degrees), underwent emergency surgery, and one of them (4.3%) died from severe heart failure. The synergistic effects of the combined antibiotic therapy were not ascertained in the present series. It was noteworthy that a bolus intravenous administration of penicillin was more effective than its continuous drip infusion. Both patients with aureus staphylococcal endocarditis died before surgery. One patient with prosthetic valve endocarditis due to candida died after a second operation. It is concluded that most patients with active infective endocarditis can be medically treated successfully, but surgery should be performed urgently for patients with severe heart failure, poor response to antibiotics, aureus staphylococcal and candida endocarditis and prosthetic valve endocarditis.