Background: The objective of this study was to correlate the V617F mutation of the JAK2 gene and the W515 mutation of the MPL gene in patients with chronic myeloproliferative disease (CMPD) with clinical parameters. Patients and Methods: 51 patients were analyzed: 31 with essential thrombocythemia (ET), 20 with polycythemia vera (PV) and 2 with primary myelofibrosis (PMF). 1 patient had unclassifiable CMPD (CMPD-U). 3 patients had overlapping features of ET and PV. Results: 31 patients (14 with PV, 19 with ET, 3 with concomitant ET and PV, and 1 with PMF) showed the JAK2 mutation, and 2 patients with ET the W515 mutation. There were no significant differences in hematocrit at diagnosis in JAK2-nonmutated versus -mutated patients with PV. Also, patients with ET had comparable platelet counts at diagnosis. The mean time from diagnosis to initiation of first therapy was similar for all patients with non-mutated versus mutated JAK2. Patients with ET and mutated JAK2 were significantly older at diagnosis than those with the wildtype gene (65.5 years vs. 54.4 years; p = 0.016). Conclusions: JAK2 V617F or MPL W515 mutations do not seem to correlate with simple clinical parameters. ET patients with wild-type JAK2 were significantly younger at diagnosis.