Background: Apparently, there is a relationship between human Herpesvirus 8 (HHV-8) infection and Kaposi´ sarcoma, especially in HIV-positive population. Objectives: To define the relationship between seropositivity against HHV- 8 and Kaposi´ sarcoma in an HIV positive and negative population from Medellin, looking for its relationship with different variables. Methods: It is a descriptive, cohort, prospective study which included sera from 98 HIV-positive and negative patients from different health institutes in Medellin. Sera were divided in 4 groups to determinate, by immunofluorescence, their seropositivity against HHV-8 and look for univariate and bivariate association with different variables. Results: We studied 98 sera. In patients with Kaposi´ sarcoma and HIV 83.3% were positive for HHV-8, in patients without Kaposi´ sarcoma but with syphilis 20.8% were positive for HHV-8, in patients without Kaposi´ sarcoma but HIV-positive 8% were positive for HHV-8, and in blood donors 4% were positive for HHV-8. The presence of KS did not have any relationship with HIV evolution and CD4 cells count. Conclusions: We have HHV-8 in our city, and there is a relationship between this virus infection and Kaposi´ sarcoma, especially in people with sexually transmitted diseases and HIV-positive patients.