Purpose of this study was to explore the epidemiological characteristics of the Dengue pathogenic serotype in patients admitted at National. Hospital of Tropical Diseases from August 2011 to July 2012. The authors confirmed that all four types of dengue are pathogenic in which the dominant type is type 2 (64.4 percent), followed by type 1 (25.4 percent), type 3 (3.4 percent), subtype 4 (3.4 percent), and the coinfected type 1 and 2 (3.4 percent). Viruses were isolated from April to November, at peak from July to October, all 4 types of dengue were confirmed. There was no significant difference in gender (p 0.05 in which 71.2 percent are between 20 to 39 years old and 91.5 percent of the patients live in Hanoi. In conclusion, in Ha Noi, all 4 Dengue serotypes were pathogenic and the disease tends to spread to the community. There is a need to monitor DHF in the upcoming years.