We report the final two-year end-of-study results from the first clinical trial investigating combination treatment with ruxolitinib and low-dose pegylated interferon-α2 (PEG-IFNα2). The study included 32 patients with polycythemia vera (PV) and 18 with primary- or secondary myelofibrosis (MF); 46 patients were previously intolerant or refractory to PEG-IFNα2. The primary outcome was efficacy, based on hematological parameters, quality of life measurements, and JAK2 V617F allele burden. We used the 2013 ELN and IWG-MRT response criteria, including response in symptoms, splenomegaly, peripheral blood counts, and bone marrow. Of 32 patients with PV, 10 (31%) achieved remission; 3 (9%) achieved complete remission. Of 18 patients with MF, 8 (44%) achieved remission; 5 (28%) achieved complete remission. The cumulative incidence of peripheral blood count remission was 0.85 and 0.75 for patients with PV and MF, respectively. MPN-SAF total symptom score decreased from 22 (95%CI, 16-29) at baseline to 15 (95%CI, 10-22) after two years. The median JAK2 V617F allele burden de-creased from 47% (95%CI, 33-61%) to 12% (95%CI, 6-22%), and 41% of patients achieved a molecular response. The drop-out was 6% for PV patients and 32% for MF patients. Of 36 patients previously in-tolerant to PEG-IFNα2, 31 (86%) completed the study, and 24 (67%) of these received PEG-IFNα2 throughout the study. In conclusion, combination treatment improved cell counts, reduced bone marrow cellularity and fibrosis, decreased JAK2 V617F burden, and reduced symptom burden with acceptable toxicity in several patients with polycythemia vera or myelofibrosis. #EudraCT2013-003295-12.