Octamer-binding transcription factor 4 (Oct4) plays a critical role for maintaining pluripotent and the self-renewing state of stem cells. Recent studies demonstrated that Oct4 gene was expressed in human cancers. Six pseudogenes of Oct4 have been proposed by using bioinformatics approach to analyze the genomic nucleotide sequences. Here, we reported that an Oct4 pseudogene localized in human chromosome 10 (Oct4-pg5) and a pseudogene in chromosome 8 (Oct4-pg1)were transcribed in cancer cell lines as well as cancer tissues tested, and the), were not found transcribed in embryonic carcinoma cells, human fibroblasts, and normal tissues tested. Our results suggest that pseudogenes Oct4-pg5 and Oct4-pg1 may be involved in the regulation of Oct4 gene activity thus Might be pertinent to carcinogenesis. Transcription of these Oct4 pseudogenes may have contributed artifacts to the current knowledge of Oct4 gene expression and function in cancers. (c) 2005 Elsevier Inc. All rights reserved.