There is serious concern about cancer risk in women undergoing ovarian stimulation treatment for infertility and longterm safety of these procedures. Association between fertility drugs and ovarian cancer is still controversial. A 30-year-old woman was referred to our institution with the initial diagnosis of an adnexal tumor after in vitro fertilization. Her history revealed adnexectomy for mucinous cystadenofibroma of the left ovary eight years ago, and cystectomy due to cystadenoma of the right ovary three years ago. At admission, the most remarkable findings were high temperature and elevated white blood cell count and erythrocyte sedimentation rate. Broad spectrum antibiotic treatment was initiated. Six days after admission, the patient was feverish, with temperature up to 38 degrees C, and evident signs of the acute abdomen. Immediate laparotomy was performed and multilocular right adnexal tumor 150x130x100 millimeters in size was identified. The right salpingo-oophorectomy was carried out. Pathological diagnosis was mucinous ovarian adenocarcinoma. Eighteen days later, radical surgery was performed. After the surgery, chemotherapy was applied. There is an urgent need for clear interpretation of the association between fertility drugs and subsequent higher ovarian cancer risk. Lacking conclusive evidence, an increased risk of ovarian cancer has been reported and more recently disputed. Higher ovarian cancer risk may be serious and even life-threatening complication for women undergoing ovarian stimulation.