Although benign uterine leiomyomata (LMA) is the most common reproductive tumor in premenopausalwomen, its etiology is largely unknown. We aimed in the present study to demonstrate the potential role ofenvironmental factors with estrogenic activity in tumor etiology by focusing on the role of aryl hydrocarbonreceptor (AhR) which mediates the effects of many environmental endocrine disruptors and contributes tothe loss of normal ovarian function in polluted environments. This case-control study aimed to compare theinteractions between AhR and lifestyle factors in a clinical setting for the first time among 138 newly diagnosedLMA patients and 138 normal controls who lived in Tehran and Mashhad, respectively, during the last 10 years.To conduct immunohistochemical studies using appropriate monoclonal antibodies, 30 cases were selectedretrospectively from 2009-2011 from the pathology departments of two university hospitals in Tehran. Althoughthe levels of sex steroid receptors were similar in adjacent myometrium and uterine leiomyomas of all cases, AhRwas significantly overexpressed (p=0.034, OR=1.667) in uterine LMA and this overexpression was correlatedwith living in Tehran [(p=0.04, OR=16 (1.216-210.58)], smoking[P=0.04, OR=2.085 (1.29-3.371)], living nearpolycyclic aromative hydrocarbon producing companies [p=0.007, OR=2.22 (1.256-3.926)] and eating grilledmeat [p=0.042, OR=1.28 (1.92-3.842)]. Our study contributes to the understanding of the effects of EDCs onAhR levels as well as women’s health and points out possible risk factors for the development and growth ofuterine LMA. It seems that the development of LMA could be the result of interactions between hormonal andenvironmental factors.