Dengue virus (DEN) is responsible for an important viral disease in the tropics. The mechanisms involved in the pathogenesis of DEN infection remain unsolved. Previous reports showed an increased level of circulating cytokines and soluble receptors in infected patients. Then an investigation of cytokines release from infected cells becomes crucial. The aim of this work was to study MIF, a pro-inflammatory cytokine related with inflammatory diseases, release during DEN2 and DEN3 infection. Plasma from DEN3-infected patients from Hospital de Clínicas de Niterói/Hospital Espanhol-RJ and cell culture of two primary targets of DEN infection, human macrophage (MO/Mø) and hepatocytes were used. MO/Mø were isolated from peripheral blood from healthy donors on Ficoll gradient, cultivated in DMEM with 10% of human serum and used after 7 days of differentiation. HepG2 cells, a human hepatoma lineage, were cultivated in MEM with 10% of bovine fetal serum. MO/Mø and HepG2 were infected with DEN2/DEN3, heat-inactivated virus (IV) or mock infected and the assays were performed in different times. MIF and TNFa in cell supernatants or patients serum were quantified by ELISA. DEN replication was quantified by Real-Time PCR assay. Cell viability was measured by MTT assay. Serum analyses showed an increase in plasma levels of MIF in DEN3 infected patients (median @5000 pg/mL) when compared to healthy donors (median @300 pg/mL). MO/Mø DEN2/DEN3 infection promotes an increase of 100% in MIF release 24 and 48 hours post-infection and more than 100% of TNFµ secretion when compared to IV and mock values. In HepG2, infection DEN2 or IV showed an increase in @ 40% in MIF release when compared to mock values 72h post-infection. No TNFa secretion was observed in HepG2 DEN2 infection. MO/Mø viability was reduced in about 25% and 75% only after 48h of DEN2 and DEN3 infection, respectively. HepG2 viability was not affected until 72h of DEN2 infection. The high leves of MIF in the plasma of DEN3 infected patients and its release from infected MO/Mø and HepG2, suggest an involvement of MIF in DEN virus infection. The reduction of MO/Mø viability occurs only after MIF release, showing a possible relation of MIF and DEN infection progression. TNFa release in MO/Mø is concomitant with MIF release. Only IV interaction with HepG2 was sufficient to induce MIF release. This suggests a different mechanism to MIF increase in DEN infected MO/Mø and HepG2. Supported by CNPq and FAPERJ.