Cancer stroma is thought to play an important role in tumor behavior, including invasion or metastasis and response to therapy. Cancer stroma is generally thought either to be non-neoplastic cells, including tissue-marrow or bone-marrow-derived fibroblasts, or to originate in epithelial mesenchymal transition of cancer cells. In this study, we evaluated the status of the p53 gene in both the cancer cells and the cancer stroma in epithelial ovarian cancer (EOC) to elucidate the origin of the stroma. Samples from 16 EOC patients were included in this study. Tumor cells and adjacent nontumor stromal cells were microdissected and DNA was extracted separately. We analyzed p53 sequences (exons 5-8) of both cancer and stromal tissues in all cases. Furthermore, we examined p53 protein expression in all cases. Mutations in p53 were detected in 9 of the 16 EOCs: in 8 of these cases, the mutations were detected only in cancer cells. In 1 case, the same mutation (R248Q) was detected in both cancer and stromal tissues, and p53 protein expression was detected in both the cancer cells and the cancer stroma. Most cancer stroma in EOC is thought to originate from non-neoplastic cells, but some parts of the cancer stroma might originate from cancer cells.