Abnormalities of platelet-function, particularly decrease of platelet aggregation, in myeloproliferative disorders have been already reported in Part 1 of this study. In this paper author studied a relationship between these abnormalities and Adenine Nucleotides (AN) in platelets. Materials were 26 cases of chronic myelocytic leukemia and 4 cases of polycythemia vera. AN in platelets (ADP, ATP) and released-AN (ADP, ATP) from platelets were assayed by Luciferin-Luciferase method. As results followings were obtained. In these myeloproliferative disorders, not only contents of ADP and ATP in platelets but also released-ADP and ATP have been significantly decreased. Furthermore, these cases have been classified into two groups: (i) cases, which showed decreased platelet aggregation and decrease of released-ADP and ATP due to decrease of contents of ADP and ATP in platelets. (ii) cases, which showed decreased platelet aggregation and decrease of released-ADP and ATP inspite of normal ADP and ATP contents in platelets. These results were thought to suggest that hemostatic abnormalities in myeloproliferative disorders might be classified into two categories, namely "Storage pool disease" and "Aspirin like release defect".