Herpes simplex virus (HSV) has been described as cause of acute tonsillitis. It has also been found in nasopharyngeal florid lymphoid infiltrate, mostly composed of CD4+, CD56+ T-cells, simulating lymphoma. In spite of its widespread prevalence in latent form, to the best of our knowledge no study is available on in situ detection of HSV in chronically hyperplastic nasopharyngeal lymphoid tissue. The purpose of the present study was to search for the presence of HSV 1 and 2 in 21 adenoids and 15 tonsils from children (2-12 years of age) in which these organs had been surgically removed due to hypertrophy. Paraffin wax-embedded sections from the 36 cases were submitted to the in situ hybridization technique, using the biotinilated probe to Herpes simplex virus 1 and 2 (Pan Path, Amsterdam) and the Rembrandt Universal DISH & HRP Detection Kit (Pan Path, Amsterdam). Positive control consisted of a previously tested Herpes infected lung. In none of the 36 cases studied were positive nuclei detected in adenoid and tonsils, either in lymphoid, in stroma or in epithelial cells, as those seen in the positive control. HSV does not seem to be implied in tonsil or adenoid chronic lymphoid hyperplasia. These organs do not seem to harbor the virus latently, or the amount of virus is too low to be detected without amplification methods.69345-9