Six cases of ovarian fibrous stromal neoplasm were studied clinically, light microscopically and ultrastructurally for the clinico-pathological evidences of hormone production. Of the six cases, two cases were fibroma, three cases were fibrothecoma, and one case was thecoma. Two cases of fibroma and one fibrothecoma were associated with clinical history of menstrual abnormality, however fat staining of the tumor was negative or weakly positive. Two cases of fibrothecoma and one thecoma were negative for the clinical history of hormone imbalance. Fat stain of those cases revealed positive in varying intensity. Ultrastructural examination of fibroma-thecoma group revealed dark and pale cells by their nuclear characteristics. The dark cells had indented nucleus and abundant cytoplasmic organelles of rough ER, Golgi apparatus and mitochondria. Intracytoplasmic cisternal spaces were seen in the dark cell cytoplasm and some lipid droplets were seen around the cisternae. Pale cells had pale swollen nucleus and fine chromatins. Their cytoplasm showed scanty amount of organelles. Fibroma-thecoma spectrum showed varying degree of population of dark cells, light cells and intervening collagenous stroma. Lipid droplet was structurally associated with intracytoplasmic cisterna and they were frequently seen in thecoma and two of the fibrothecoma. But clinical history of hormone imbalance was poorly related to the light microscopic morphology and ultrastructural organization.