Researchers will use abnormal blood and/or bone marrow cells, or materials derived from these abnormal cells, like DNA, RNA, protein or plasma, in laboratory studies. Toenail clippings will provide normal material like DNA for comparison with the abnormal material derived from the blood and/or bone marrow. The results of these studies will be correlated with subjects' disease symptoms and response to their experimental treatment. The MPD-RC researchers are interested in studying molecules from the blood and bone marrow, the exact molecules changing over time with the investigators choosing only the most promising for investigation.

The investigators are attempting to better understand the causes of MPD and to develop improved methods for the diagnosis and treatment of these diseases. These syndromes carry a high risk of developing leukemia. It is important to continue to learn more about these blood cancers and to learn more about the effectiveness and potential side effects of various treatments. It is believed that further basic knowledge about these cancer cells as well as the effects of treatment will lead to the improvement of current therapies and the development of entirely new treatments for these diseases. The MPD-RC is hoping to determine if a number of laboratory tests (biomarkers) will allow for the prediction of response in future patients to the treatment they would receive.

Inclusion Criteria:

• Patients are to be registered to this study if they meet the eligibility criteria for one of the MPD-RC treatment protocols linked to this study.
• Patients diagnosed with the following Myeloproliferative disorders including: polycythemia vera (PV), idiopathic myelofibrosis (IM), and essential thrombocythemia (ET) who are participating in treatment protocols of the MPD-RC are eligible.
• Patients must have signed an informed consent to participate in a Myeloproliferative Disorders Research Consortium (MPD-RC) treatment study to which this protocol is a companion study. The subject must also have signed a consent to participate in this mandatory companion study.

Exclusion Criteria:

See inclusion criteria.

Subjects enrolled in MPD-RC treatment protocols.