A cystic lesion of the spermatic cord resembling an ovarian serous epithelial tumour of low malignant potential or borderline malignancy is reported. Immunohistochemical staining and electronmicroscopic examination suggested epithelial rather than mesothelial differentiation of the cyst lining cells. There was strong positive immunohistochemical staining of cyst lining cells for CA 125, providing evidence for Müllerian differentiation. A flow cytometric analysis of nuclear DNA content revealed a diploid profile.