Kaposi's sarcoma (KS) is caused by Kaposi's sarcoma associated herpesvirus, the eighth Herpesvirus found to infect humans (KSHV/HHV 8). KSHV seroprevalence and its genetic diversity have been shown to be mainly related to ethnic background and geographical localization. Very scant information on the KSHV seroprevalence and its variants distribution is available for Brazil. There are increasing concerns related to public health priorities to define whether KSHV, an oncogenic Herpesvirus, should be screened in blood centres. This thesis combined Epidemiology and Molecular techniques to shed some light on the risk factors associated with KSHV infection in populations at low-risk for sexually transmitted infections and to describe the genotypes of KSHV DNA based on the genetic variability concentrated on the variable fragments VR1 and VR2 of the ORF K1 amplified from selected populations. An analytical cross-sectional study was conducted to estimate the seroprevalence of, and risk factors associated with KSHV infection in the three largest cities of 3 of the 5 main regions of the country: i.e. Sao Paulo (South-East), Salvador (North-East) and Manaus (North), chosen to represent the geographical and ethnic diversity of Brazil. KSHV antibodies were detected using a previously validated testing strategy by using a combination of statistical approaches useful to evaluate a new diagnostic test when a gold standard is not available. The seroprevalence of HSV-2, a sexually transmitted herpesvirus, was determined as a proxy estimation of sexual behaviour of studied population. The genetic diversity of KSHV/DNA was described, based on the amplification of the variable fragments of KSHV ORF K1 detected in KS tumour tissue from AIDS-KS patients and seropositive blood donors. We found a high seroprevalence of KSHV infection amongst Brazilian blood donors (25%). Phylogenetic analysis revealed that KSHV/DNA variants amplified in this study clustered as subtypes A, B and C.