It has been suggested that Oct-3/4 may regulate self-renewal in somatic stem cells, as it does in embryonic stem cells. However, recent reports raise the possibility that detection of human Oct-3/4 expression by RT-PCR is prone to artifacts generated by pseudogene transcripts and argue against a role for Oct-3/4 in somatic cells. In this study, we clarified Oct-3/4 expression in mouse somatic tissues using designed PCR primers, which can exclude amplification of its pseudogenes. We found that novel alternative transcripts are indeed expressed in somatic tissues, rather than the normal length transcripts in germline and ES cells. The alternative transcripts indicate the expression of two kinds of truncated proteins. Furthermore, we determined novel promoter regions that are sufficient for the expression of Oct-3/4 transcript variants in somatic cells. These findings provide new insights into the postnatal role of Oct-3/4 in somatic tissues.