Ovarian stromal and or sex cord tumors develop from the supportive tissue of the ovaries. Within this group of tumors, we distinguish granulosa tumors, androblastomas(Sertoli Leydig tumors), sex cord tumors with annular tubules, steroid cell tumors and fibrosarcomas. Most of these tumors synthesize ovarian hormones: estrogens, androgens and corticosteroids. Sertoli Leydig tumors are almost always benign, while others are malignant with locoregional recurrences. Their prognosis is uncertain. The poorly differentiated forms of Sertoli-Leydig tumors have a significant potential for malignancy. We report the case of a 45-year-old patientwith a large non-secreting ovarian tumor, whose biopsy suggested a Sertoli-Leydig tumor, of intermediate differentiation. We decided to perform surgical excision, which revealed a tumor at the stage of peritoneal carcinomatosis. And a cytoreductive procedure was performed. Surgery is the mainstay of treatment, and should be supplemented by chemotherapy in case of malignancy.