BACKGROUND AND PURPOSE: To evaluate whether cisplatin-induced stroke is mediated by vascular toxicity with release of prothrombotic endothelial and platelet-derived microparticles (MPs). METHODS: Endothelial (CD31(+)CD41(-)), platelets (CD31(+)CD41(+)) and prothrombotic (Annexin V(+)) circulating MPs were quantified by flow cytometry in 18 patients with cancer, before and 3 days after administration of cisplatin, and compared with 18 healthy controls. Thrombin-antithrombin complex and prothrombin fragments (F(1+2)) were measured as markers of the activation of the coagulation. RESULTS: In patients with cancer, baseline levels of circulating prothrombotic, endothelial and platelet-derived MPs were similar to healthy controls and decreased significantly after administration of cisplatin. High-baseline MPs levels were observed in 5 patients who received cisplatin for a second or third cycle. A high-baseline activation of the coagulation was observed in all patients without further increase after cisplatin infusion. CONCLUSIONS: Cisplatin treatment is immediately followed by a decrease in circulating levels of endothelial and platelet-derived MPs. However, a transient increase in MPs is observed at the second and third infusion, and this may contribute to the cisplatin-induced stroke.