Cytoreductive surgery has traditionally been regarded as a cornerstone in the primary treatment of advanced ovarian cancer. Both five year survival and median survival are better for patients with small residual masses. Despite many similar reports showing the prognostic significance of postoperative residual tumour, the survival benefits of cytoreductive surgery still remain scientifically unproven and controversial. There have been no prospective controlled clinical trials. The question remains as to whether the observed survival benefits for patients subjected to primary cytoreductive surgery are an effect of surgery skills or tumour biology. The proponents of tumour biology claim that cytoreductive surgery is a selective procedure and that patients with better prognosis are selected. Therefore a randomized study between primary cytoreduction and neoadjuvant chemotherapy in patients that cannot be optimally cytoreduced seems warranted, though one problem with such a study is how to select eligible patients. During chemotherapy and after relapse several types of operations are used in ovarian cancer: secondary cytoreductive surgery, interval cytoreductive surgery, second-look surgery and palliative secondary surgery. So far interval cytoreductive surgery during chemotherapy is the only type of operation which in a prospective randomized study showed significant improvement in long-term survival. This paper discusses indirect evidence in the literature in support of or in contradiction to the primary debulking hypotheses and also indications and impact of surgical procedures during chemotherapy.