Purpose: The purpose of this study was to investigate the effects of aromatherapy on stress, fatigue, mood, and vital signs of the nurses in the operating rooms. Methods: The data were collected from September 2007 to February 2008 in the operating room at K hospital located in Seoul, Korea. A total of 48 nurses were recruited. Among them, 25 nurses were randomly assigned to an experimental group and 23 were assigned to a control group. Experimental group was provided with aroma inhalation by necklace which had essential oil mixture of 0.2 cc. For aroma inhalation, Lavender, Zeranium and Mazoram were mixed in ratio of 5:3:2. In order to test the effectiveness of aroma inhalation, the pretest and posttest results for stress, fatigue, mood, and vital signs were compared between the experimental group and the control group. The data were analyzed by unpaired t-test and ANCOVA using the SPSS/WIN 15.0 program. Results: There were statistically significant decreases in the stress and fatigue scores, and increase in the mood scores and showed significant relaxation in the vital signs after the aroma inhalation. Conclusion: The aromatherapy had the positive effects on stress, fatigue, mood, and vital signs.