Recently several papers have been published on the use of vancomycin (VCM) to prevent perioperative infection during open-heart surgery, but there have been few papers from Japan. In this study, we evaluated the pharmacokinetics of VCM in the serum and right atrial tissues of eight patients (4 men and 4 women) who underwent open-heart surgery, to prevent perioperative infection. Preoperatively all patients had neither hearing disorder nor renal dysfunction. A total of 1, 000mg of VCM was given intravenously over 40-50 minutes before a skin incision. The serum levels of VCM were measured every 20 minutes during open-heart surgery with enzyme-immunoassay. VCM levels in the right atrial tissues were also assayed before the start of extracorporeal circulation (ECC). The peak serum levels of VCM were 55.3±10.1μg/ml and decreased gradually to 10μg/ml prior to the ECC. During the ECC, the serum levels of VCM remained between 7.6 and 9.9μg/ml, while VCM levels in the right atrial tissues were 18.9±6.9μg/ml (serum/tissue ratio: 0.34). Staphylococcal infection is generally inhibited by VCM levels of 2.0-6.5μg/ml. This study suggests that 1, 000mg of VCM given intravenously before a skin incision may be effective to prevent perioperative infection during open-heart surgery.