Although a number of agents have been used to treat these diseases, most patients do not respond to treatment. Imatinib has been shown in clinical trials to induce high rates of responses in patients with chronic phase CML. Imatinib has also been shown to be effective in inducing responses in a subset of patients with CMML and atypical CML and is also effective in a subset of patients with idiopathic hypereosinophilic syndrome (HES), another myeloproliferative disorder. Because patients with several different myeloproliferative diseases have been shown to experience dramatic responses to imatinib, we would like to determine what proportion of patients with atypical myeloproliferative diseases (CMML and atypical CML) will respond to this agent.