OBJECTIVES: Results on the prognostic value of human epidermal growth factor receptor 2 (HER-2)/neu in ovarian cancer are inconsistent. This exploratory analysis evaluates Her-2/neu as a prognostic factor in a large cohort of patients with advanced-stage ovarian cancer treated with platinum/paclitaxel as first-line chemotherapy within a prospective randomized trial. METHODS: Her-2/neu expression was assessed by immunohistochemistry in 359 patients (46%) treated within the AGO-OVAR 3 trial (n = 783). Patients received either cisplatin/paclitaxel or carboplatin/paclitaxel according to the study protocol. Immunohistochemistry results were scored according to the Dako score. RESULTS: Her-2/neu Dako scores of 0 or 1+ was found in 337 patients (94%) and a score of 2+ or 3+ in 22 patients (6%). Her-2/neu overexpression (2+/3+) was associated with a higher International Federation of Gynecology and Obstetrics stage and larger postoperative residual disease. There were no significant differences in response to chemotherapy between the Her-2/neu score subgroups and in progression-free survival time. In a multivariate analysis, the Her-2/neu score had no significant impact on overall survival time. CONCLUSIONS: In the present study, Her-2/neu overexpression in patients with advanced-stage ovarian cancer was rare and provided no evidence for a prognostic value of Her-2/neu in patients with advanced ovarian cancer treated with platinum/paclitaxel.