Human herpesvirus 6 (HHV-6) is a recently discovered virus which has not been causally linked to any particular disease. In order to investigate the possible role of this virus in the pathogenesis of lymphoid malignancies, we examined tissue samples from 117 patients for the presence of HHV-6-specific DNA sequences. Two cases of non-Hodgkin's lymphoma were found to be positive. One patient had a T cell lymphoma and a preceding history of angioimmunoblastic lymphadenopathy; the other had a B cell lymphoma occurring in the context of Sjögren's syndrome. HHV-6 has been isolated previously from a patient with angioimmunoblastic lymphadenopathy, and viral sequences have been identified in another patient with Sjögren's syndrome and B cell lymphoma. The relationship between HHV-6 and these conditions therefore warrants further investigation.