The thrombotic and hemorrhagic diathesis represents a frequent complication in myeloproliferative disorders (CMPD). They are correlated with the number of platelets, but also with their qualitative disorders, such as membrane glycoprotein changes. The latter are revealed by many platelet essays including flow-cytometry and include modified activation, secretion and aggregation patterns. The thrombopoietin platelet receptor (cMPL), affected by the JAK2 V617 mutation encountered in CMPD, may be associated with a prothrombotic status. Its implication reveals the importance of the molecular genetics profile in defining molecular diagnostic hallmarks and makes it a candidate in the early diagnosis of myeloproliferative disorder and a predictor of thrombotic complications in this group of diseases.