Background. Preoperative anxiety can lead to unfavorable physiological response such as tachycardia and hypertension. Prevention of preoperative anxiety improves surgical outcome and decreases inpatient stay. Yokukansan is one of prescriptions in Kampo, traditional Japanese herbal medicine, and is known to exert anxiolytic effects. The aim of the present study was to compare the effects of diazepam and Yokukansan on preoperative anxiety, salivary amylase activity, and sedation levels. Methods. Seventy American Society of Anesthesiologists physical status I or II patients presenting for hemicolectomy under general anesthesia combined with epidural anesthesia were enrolled. The Diazepam group received diazepam 5 mg orally and the Yokukansan group received Yokukansan 2.5 g orally. Results. Although levels of anxiety and salivary amylase activity were not different between the two groups, the modified Observer's Assessment of Alertness/Sedation Scale of the Yokukansan group was significantly higher compared to that of the Diazepam group. Conclusion. Yokukansan alleviated preoperative anxiety without undesirable sedation, when compared with diazepam.