Epstein-Barr Virus is an important aetiological factor in the development of nasopharyngeal carcinoma (NPC). Serology suggested that besides NPC some other tumours located within the lymphoepithelial ring of the throat (Waldeyer's ring) might be associated with EBV. Nucleic-acid hybridizations were carried out to detect the presence of EBV-DNA in tumour biopsies derived from tonsillar carcinomas. We were able to demonstrate the presence of EBV-DNA in the tumour cells of two poorly differentiated carcinomas. We think that only a small fraction of tonsillar carcinomas is positive for EBV. The aetiologic relationship of EBV with tumours of Waldeyer's ring is discussed.