Myeloproliferative neoplasms are frequently complicated by thrombosis and bleeding. Therefore, not only their primary prevention, but also the management of special clinical issues is important. These issues include venous thromboembolic disorders such as splanchnic venous thromboembolism, as well as major bleeding, surgery, and pregnancy. As for the primary prevention of thrombosis, it has been proposed that low-risk essential thrombocythemia with newly reported risk factors (cardiovascular risks or JAK2V617F) might be included among the factors meriting prevention. As for management of the aforementioned special clinical issues, an expert consensus has been established, wherein the recommended treatment strategies are described. In Japan as well, clinical practice based on this consensus would be preferable.