Surgery is the essential element of staging and treatment of malignant ovarian tumours. Regardless of the stage, it must include peritoneal cytology, hysterectomy with bilateral adnexectomy, omentectomy, pelvic and lumbo-aortic lymphadenectomy, appendicectomy and multiple peritoneal biopsies. In stage I tumours, in young women desiring a subsequent pregnancy, preservation of the uterus and contralateral ovary can be proposed. In stages II, III and IV, the therapeutic strategy consists of primary surgery and systematic chemotherapy (6 cycles). Radical surgery is essential in these cases, as the size of the residual tumour at the end of operation constitutes the major prognostic factor. To optimize the quality of tumour debulking, the maximum of visible carcinomatous nodules must be resected with, if necessary, gastrointestinal resections. The value of second-look surgery, after 6 cycles of chemotherapy, is currently controversial: it is only indicated in the context of randomized trials. Borderline malignant ovarian tumours have a good prognosis regardless of their stage. Surgery can very often be conservative, particularly in young women. Adjuvant chemotherapy has been shown to be effective in these tumours. Many studies are underway to define the value of new cytostatic molecules and "interval" surgery (intercalated between several courses of chemotherapy).