Plasma cytokine milieu is abnormal in primary myelofibrosis (PMF) and correlates with disease phenotype and prognosis. In this study, we show that several plasma cytokines are also abnormally expressed in polycythemia vera (PV; n = 65), compared to normal controls (n = 35), but with a significantly different pattern than that of PMF (n = 127). Direct phenotypic correlation in PV included levels of IL-12 with hematocrit; IL-1b, IL-2, IL-7, FGF-b, and HGF with leukocytosis; and IFN-α and IFN-γ with thrombocytosis. In univariate analysis, levels of 13 cytokines (out of 30 analyzed) correlated with survival but only MIP-1β remained significant on multivariable analysis that included the other cytokines as covariates. Increased level of MIP-1β (P < 0.01), older age (P < 0.01), and leukocytosis (P = 0.03) maintained their association with shortened survival, on multivariable analysis. This study provides preliminary observations that warrant a larger scale study and suggests the value of plasma cytokines as prognostic biomarkers in PV. Am. J. Hematol., 2012. © 2012 Wiley Periodicals, Inc.