Epstein-Barr virus (EBV) is a gamma DNA herpes virus which is thought to play a part in the pathogenesis of some non-Hodgkin's lymphomas in individuals with or without immunodeficiency. We investigated 16 lymph nodal and 12 cutaneous anaplastic large cell lymphomas (ALCLs) (Ki-1+), all of which were in patients without immunodeficiency, for the presence of EBV genomes. The highly sensitive polymerase chain reaction (PCR) technique was employed for detection of viral DNA in extracts from formalin-fixed, paraffin-embedded tissue sections. In addition, we performed radioactive and non-radioactive in situ hybridization (ISH) for localization of EBV at the single cell level. EBV-DNA was demonstrated by PCR in five cases of nodal ALCLs (31%). All cutaneous ALCLs were negative. EBV-encoded small nuclear RNAs (EBERs) could be identified by ISH in the tumour cells of one of the five EBV-DNA-positive patients. Our results further support the concept that EBV may be involved in the development of a proportion of nodal ALCLs, but not in cutaneous ALCLs.