We investigated 26 B-cell post-transplant lymphoproliferative disorders (B-PTLD) and 15 human immunodeficiency virus-related aggressive B-cell lymphomas (HIV-BCL) from England that were associated with Epstein-Barr virus (EBV) for the polymorphic sequences of the EBV-encoded nuclear antigen 3C (EBNA3C) gene to distinguish the two different EBV strains. Type-A-EBV was identified in 92% of B-PTLDS and in 53% of HIV-BCL (P = 0.003). Among HIV-BCL, patients associated with type-B-EBV had been HIV positive for significantly longer when compared to those associated with type-A (P = 0.037) although there were no correlations with ethnicity, CD4 cell counts or plasma HIV viral load.