Tobacco-smoking is one of the well understanding carcinogenic factors involved in breast cancer formation.In this study, we first demonstrated that the several types of nicotinic acetylcholine receptors (nAchRs) were detected in breast cancer cell lines including MCF-7 and MDA-MB-231.The expression of the nAchR mRNA levels in tumor tissues from 157 cases of breast cancer patients in Taiwan were determined and found that the α5, and α9 subunits of the nAchRs were the most prevalence in both normal and tumor tissue.Quantitative assays of the nAchRs mRNA levels was performed by real-time PCR analysis which revealed that the expression levels of α9-nAchR was higher in most of the tumor tissue when compared to the normal tissues which dissected form the tumor margin.