Using the polymerase chain reaction (PCR) to analyze paraffin sections from 12 Caucasian patients, we detected only the prototype F Epstein-Barr virus (EBV) in 10 specimens from patients with nasopharyngeal carcinoma (NPC). This is in contrast to the higher frequency of association of "f" variants in NPC biopsies from Southern Chinese. The results of EBV genotyping support evidence that the EBV strains associated with NPC in the Southern Chinese population differ from those found in Caucasians. DNA sequencing confirmed that a simple point mutation is responsible for the restriction-fragment-length polymorphism which distinguishes the prototype F virus from the "f" variant.