Background: Maximum cytoreduction at primary surgery has been found to be one of the strongest prognostic factors for survival of ovarian cancer. The aim of the study was to investigate the influence of hospital level (primary vs secondary care centre), number and timing of surgery and chemotherapy on how radical the surgery was at primary treatment of epithelial ovarian cancer Stage IIIC. Material and Methods: A retrospective study based on record information from all patients with epithelial ovarian cancer Stage IIIC treated at the Norwegian Radium Hospital (NRH) 1985-2000, in total 776, subdivided into four groups: 1) Local primary surgery, no direct re-operation at NRH, no interval debulking; 2) local primary surgery, no direct re-operation, but interval debulk­ing after 3-4 courses of chemotherapy at NRH; 3) local primary surgery, direct re-operation at NRH, no interval debulking; 4) primary surgery at NRH. Lymph node biopsies at re-operation in early stages and upgrading of stage where necessary were regis­tered. Results: Whether surgery was radical or not was an independent prognostic factor for overall and progression-free survival. The treatment group was an independent prognostic factor for overall, but not for progression-free survival. Group 3 had significantly the best overall and progression-free survival (p = 0.01 and 0.05). For macroscopically radical surgery both overall and progression­free survival were found significantly better for groups 3, 4 and 1 than for group 2. Most lymph node biopsies were performed during the last period and 28% were upgraded from Stage I and II to IIIC. More patients were referred for primary surgery at NRH during the last 5-year period during which overall survival and time to progression were significantly better. Interpretation: Whether primary surgery is radical or not is a significant prognostic factor for survival and primary surgery is best performed by specialists in gynaecological oncology.