Dengue hemorrhagic fever (DHF) is an acute epidemic diseases which require a good clinical examination and complete, as well as laboratory investigations if clinical symptoms is inadequate. Delay in diagnosis result in increased risk of death. This research is to determine the characteristics of hematology in dengue fever patients in internist unit at Arifin Achmad Riau Province Hospital at period 1 January - 31 December 2013. This research is a retrospective descriptive study of total sampling. Based on the results of the study, found patients aged 15-19 years (34.8%) and the majority are male (67.4%). Hemoglobin levels on day 3, 4, 5 continued normal fever (39.2%), normal (45.6%), and normal (47.8%). Hematocrit levels on day 3, 4, 5 continued normal fever (54.3%), normal (43.5%), and low (50%). The number of leukocytes on day 3, 4, 5 continued fever leukopenia (52.2%), leukopenia (47.8%), and normal (43.5%). Platelet count on day 3, 4, 5 continued thrombocytopenia (97.9%), thrombocytopenia (95.6%), and thrombocytopenia (97.9%). Many patients who do not carry out checks antidengue IgG and IgM antidengue (50%) and secondary dengue patients (39.13%)