Surgical treatment of active native valve endocarditis. A report is presented of 24 patients (23 male), mean age 38 years, who underwent surgery for active native valve endocarditis of the left heart in 1975-1988. The aortic valve was affected in all patients, and also the mitral valve in five. Pre-existing aortic valve disorder was present in 17 cases (13 congenitally bicuspid 4 rheumatic affection). There were five hospital deaths (20.8%). Staphylococci as causal organism and extensive infection predicted the highest mortality and morbidity. The mean follow-up time was 39.7 (range 2-114) months. Two reoperations because of prosthetic valve dehiscence revealed endocarditis of the implanted valve. Strong correlation was found between favourable postoperative course and rapid normalization of C-reactive protein levels, which did not fall in patients with persistent infection. Early surgery is recommended if the course of bacterial endocarditis is severely complicated. 