The study aim was to assess the diagnostic value of intraoperative swabs of heart valves in infective endocarditis. Among 83 patients with confirmed diagnosis of infective endocarditis referred for surgical treatment, microorganisms were isolated by a minimum of two positive blood cultures. Results were compared to those obtained with intraoperative heart valve swab cultures. In 37% of cases, the intraoperative swab confirm the preoperative diagnosis, while in 51% heart valve cultures were sterile or presumed to be contaminated. A microorganism could be cultured in three of the ten patients with preoperative culture-negative infective endocarditis. Because of a relatively high rate of presumed contaminants in heart valve cultures, the risk of inappropriate postoperative modification of the antibiotic regimen is imminent in patients with active infective endocarditis. In patients in whom the causative agent could be isolated before surgery, intraoperative valve swabs do not contribute further to patient management.