A case of diagnosis of a variety of ovarian thecoma, a thecoma with amyloidosis of the stroma, in a patient with fibromyoma of the uterus is described. Brief clinical data, characteristics of the tumor morphology including polarization microscopy and histochemistry, and differential diagnosis of forms of amyloidosis are presented. The presence of amyloid in the thecoma is considered to reflect the capacity of the tumor theca-cells of mesenchymal origin to produce amyloid.