Despite recent achievements in the therapy of primary ovarian cancer (OC), a significant number of patients still relapse. Several clinical trials have shown that maintenance therapy with conventional chemotherapeutic drugs is less effective while leading to more morbidity due to toxicity; therefore, current research is focusing on maintenance therapy with targeted agents. Multiple biologic drugs are being applied in clinical trials for both primary and relapsed OC, with bevacizumab yielding the most clinical data to date. However, biological markers predictive of successful therapy are largely missing.