Human herpesvirus 8 (HHV8) has been associated with multicentric Castleman's disease, Kaposi's sarcoma and effusion non-Hodgkin's lymphoma. Epidemiological studies have shown seropositivity in variable proportions of populations. It seems to be sexually transmitted among adults and through oral contact among children. The virus has been demonstrated in desquamating oral epithelial cells, but there is no report on its presence in the Waldeyer's ring. The purpose of the present study is to detect HHV8 in tonsils and adenoids from children up to 20 years of age in which these organs had been surgically removed due to hypertrophy, using immunohistochemistry and in situ hybridization. Paraffin wax-embedded sections consisting of 181 tonsils and 162 adenoids from 293 patients were analyzed. HHV8 was detected by immunohistochemistry (IHC) using the anti-LNA1 antibody (Novocastra) and the LSAB+ detection system (Dako). For the in situ hybridization (ISH), the T1-1 probe for the viral mRNA and the detection system used were provided by Novocastra. In 20 cases (6.83%), HHV8 was detected in cells morphologically characterized as lymphoid. In three of them epithelial cells were also positive. In 19 cases, the virus was detected in tonsils and in just 1 case in an adenoid. In all 20 cases detection was possible by ISH, whereas in only 2 of them there was a concomitant positivity by IHC. Our data support the oral route of contamination by HHV8 in children, in whom tonsils and adenoids may harbor the virus. It is found especially in tonsils and only rarely in adenoids. In these organs, ISH is the method of choice to detect this virus, probably due to the small amount of viral proteins.7065-72