Twenty eight patients with native valve endocarditis (NVE) were subjected to this study. Thirteen patients underwent an operation at the chronic phase, and 15 patients at the active phase. One of the 13 patients at the chronic phase died of cardiac rupture due to myocardial infarction which had occurred preoperatively, and one of 10 patients at active phase without annular infection died of rupture of mycotic cerebral aneurysm early postoperatively. Among 5 patients at the active phase with annular infection, prosthetic valve endocarditis occurred in one patient 1.5 months after supraannular aortic valve replacement, and the second operation with a translocation technique was needed. This patient was lost from low output syndrome. Another patient in this group, who underwent a translocation technique because of mycotic annular abscess, died of intestinal infarction late postoperatively. The other 24 patients went a good postoperative course. Five patients with annular infection at the active phase had a shorter duration from the infectious onset to operation (20 days to 2 months, average 38 days), and the causative microorganisms were streptococcus faecalis, staphylococcus epidermidis and gram-negative coccus. One patient, who died of mycotic cerebral aneurysmal rupture, had candida albicans as a causative microorganism. For patients with NVE, an early aggressive operation is essential before infection extends to the annulus or to other vital organs, especially when these microorganisms are identified.