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Background and Objective: Due to high prevalence of pre-menstrual syndrome (PMS) and pre-menstrual dysphoric disorder (PMDD) and its effect on the educational, professional activities and familial behaviors, this study was conducted to determine the prevalence of clinical manifestations of pre-menstrual syndrome and pre-menstrual dysphoric disorder in medical students. Methods: This descriptive-analytic study was done on 162 female medical students of Golestan University of Medical Sciences in Gorgan, Iran during 2010. Demographic characteristics and PMS and PMDD clinical manifestations questionnaire based on DSM-IV-TR and ACOG criteria was filled for each subject. Results: Mean age and menarche age of subjects was 22.2±2.5 and 13.3±1.2 years, respectively. 145 students (89.5%) were single. 57.4% and 22.8% of participants fulfilled the criteria of PMS and PMDD, respectively. The most frequent affective and somatic symptom was lethargy and fatigability (57.4%) followed by sensation of bloating and weight gain (45.7%). The lowest frequent somatic and affective symptoms were dyspnea (8%) and insomnia (1.2%), respectively. There was significant correlation between the prevalence of PMDD and chronical and menarche age (P<0.05). Conclusion: Pre-menstrual syndrome is a prevalent disorder in medical students of Golestan University of medical sciences in Iran.