A granulosa cell tumor in a 69‐year‐old woman was diagnosed by aspiration biopsy cytology, and different regions were further studied by light and electron microscopy. An almost continuous series of structures, from areas closely imitating normal ovarian follicles and follicular granulosa cells, to minor regions with theca‐like elements was found. The histogenesis, fine structure, and endocrine activity of steroid producing ovarian tumors was discussed, and it was concluded that feminizing or virilizing ovarian mesenchymoma is a suitable collective term for these tumors.