INTRODUCTION Ovarian cancer patients are at high risk of thrombosis particularly during chemotherapy treatment however the mechanism is not understood. The aim of this study is to investigate the role of the activated protein C (aPC) pathway in the procoagulant activity observed in ovarian cancer patients undergoing neoadjuvant chemotherapy. PATIENTS AND METHODS Thrombin generation was determined before and after addition of thrombomodulin (TM) in high grade serous ovarian cancer (HGSOC) patients treated with neoadjuvant chemotherapy (n = 29) compared with HGSOC patients who were chemo naive (n = 23) and patients with benign tumours (n = 29). Plasma expression of proteins from the aPC pathway was analysed. mRNA expression was determined in endothelial (EA.hy926) and ovarian (OAW42) cell lines following addition of carboplatin and paclitaxel. RESULTS Lower levels of ETP (p