In view of the possible antiplatelet effects of general anesthetics, we investigated the in vitro effects of desflurane, a new inhalation agent, on platelet aggregation. For 15 patients who underwent elective operations, blood was sampled with desflurane induction before and after anesthesia but prior to surgery so that platelet aggregation in the drawn blood could be tested before desflurane anesthesia and again after exposure to the anesthetic. Platelet aggregation was measured with a whole-blood aggregometer. Adenosine diphosphate (ADP), collagen, and ristocetin were used as aggregating agents. Our results showed that aggregation in response to ADP collagen, or ristocetin was not inhibited in patients who received desflurane anesthesia. This study with an in vitro model showed that desflurane had no influence on platelets in clinically relevant doses. (C) 2004 The Japanese Society of Hematology.