A retrospective survey of patients with infective endocarditis at St. Bartholomew's Hospital in the decade 1966--75 showed a male/female ratio of 1.5/1. The commonest presenting features were malaise, fever, new cardiac symptoms, heart-failure, splenomegaly, and finger clubbing. The commonest problem during treatment was heart-failure. As in the two previous decades, viridans streptococci were the commonest causative organisms. Acute endocarditis was caused by Staphylococcus aureus. 6 patients' lives were saved by heart-valve replacement during medical treatment. Of 3 patients who relapsed, 1 died. The overall mortality at six months was 20%, compared with 40% in the two previous decades. Of the patients with proven subacute infective endocarditis thought to have received adequate antibiotic treatment, only 5 of 49 (10%) died; in a similar group of patients in the previous decade 19% died. Early surgical intervention probably accounts for the improved prognosis.