Previous studies have demonstrated that pluripotency-associated transcription factors, such as Oct3/4, Nanog and Sox2, play a crucial role in the development and malignant progression of various types of tumors. Breast cancer is the most frequent cancer among females, being a heterogeneous disease, with distinct morphologies, metastatic behavior and therapeutic responses. The expression of Oct3/4, Nanog and Sox2 in 3 human breast cancer cell lines, MCF7, T-47D and MDA-MB-231, was determined. The expression of Oct3/4, Nanog and Sox2 mRNA was determined by reverse transcription polymerase chain reaction (RT-PCR) and protein expression was detected by immunocytohistochemistry. RT-PCR revealed that all three human breast cancer cell lines tested expressed evident Oct3/4, Nanog and Sox-2 mRNA at various levels. Higher levels of Oct3/4 were identified in MCF7 and MDA-MB-231 cells compared with T-47D cells. Higher levels of Nanog were observed in MCF7 and T-47D cells compared with MDA-MB-231 cells and the highest expression of Sox-2 was detected in MCF7 cells. The nuclear localization of Oct3/4, Nanog and Sox-2 was confirmed by immunostaining. Oct3/4, Nanog and Sox2 were expressed in human breast cancer cell lines. Further studies are required to characterize the role of Oct3/4, Nanog and Sox2 in human breast cancer.