Breast cancer is the most common cancer among females worldwide and a most prevalent malignancy inIranian women. Chronic stress may make an important contribution to cancer, especially in the breast. Numerousstudies showed roles of neurotransmitters in the occurrence and progression of cancers which are mediated bytheir various types of receptors. This study was conducted to evaluate alterations in the expression profile ofdopamine receptor genes in peripheral blood mononuclear cells (PBMC) as stress factors in breast cancer patientsand the human breast cancer cell line (MCF-7). Peripheral blood samples were obtained from 30 patients and30 healthy individuals. Total mRNA was extracted from PBMC and MCF-7 cells and RT-PCR was performedto confirm the presence of five dopamine receptors (DRD1-DRD5). Expression changes of dopamine receptorgenes were evaluated by real time PCR. We observed that DRD2-DRD4 in PBMCs of breast cancer patientswere increased compared to healthy individuals. In addition, all dopamine receptor subtypes but DRD1 wereexpressed in MCF-7 cells. Therefore, alterations of these receptors as stress factorsshould be assessed for selectingappropriate drugs such as D2-like agonists for treatment of breast cancer after performing complimentary tests.Determining the expression profile of dopamine receptor genes thus seems promising.