OBJECTIVE: A majority of menstruating women experience some degree of regular recurrences of diverse symptoms-commonly known as premenstrual syndrome (PMS)-during the days before menstruation. Given the multifactorial etiology of PMS, no single treatment is universally recognized as effective, and many women turn to alternative modalities, including aromatherapy. The present study investigated therapeutic effects on premenstrual symptoms using fragrance from yuzu, a Japanese citrus fruit (Citrus junos Sieb. ex Tanaka), and aromatherapy, from the perspective of autonomic nervous system function. SUBJECTS: Seventeen women in their 20s with subjective premenstrual symptoms. DESIGN: A single-blind randomized crossover study. SETTINGS/LOCATION: This study was performed at a laboratory in a university in Osaka, Japan. Subjects were examined on two separate occasions in the luteal phase. OUTCOME MEASURES: Using two aromatic stimulation sources (yuzu and lavender used as the control), this experiment measured heart rate variability (HRV) reflecting autonomic nerve activity and the Profile of Mood States (POMS) as a psychologic index before and after aromatic stimulation. RESULTS: A scant 10-min inhalation of the yuzu scent significantly decreased heart rate and increased high-frequency power of HRV, reflecting parasympathetic nerve activity, in the luteal phase. Additionally, POMS tests demonstrated that inhalation of the yuzu essential oil significantly decreased three negative subscales: tension-anxiety, anger-hostility, and fatigue-common premenstrual symptoms, together with a total mood disturbance as a global measure of affective state, as long as 35 min after the aroma stimulation. These premenstrual psychoneurophysiologic effects of yuzu fragrance did not differ from those of the effects of lavender. CONCLUSIONS: The present study indicated that short-term inhalation of yuzu fragrance could alleviate premenstrual emotional symptoms, which, at least in part, is attributable to the improvement of parasympathetic nervous system activity. This study further implies that yuzu fragrance aromatherapy might serve as an anti-PMS modality, given its comparable psychoneurophysiologic effects to those of lavender, a representative relaxing scent.