This report describes the results of histopathologic and virologic studies in six patients with undifferentiated carcinoma (malignant lymphoepithelial lesions) of the salivary glands. Epstein-Barr virus (EBV) was detected in tumors from all six patients by DNA hybridization, while adjacent non-tumorous salivary gland tissue was negative for EBV in two patients tested for DNA and in three patients tested for Epstein-Barr nuclear antigen (EBNA). These findings add more evidence that these unusual salivary gland tumors are EBV-associated, and that EBV is specific to the tumor.