Mumps virus antigens were demonstrated in biopsied tissues from Hodgkin’s disease patients by indirect immunofluorescence. Impression smears from ten lymph node and two spleen specimens revealed viral antigens in the nucleus, cytoplasm or both. Measles virus antigens were detected in six out of seven Hodgkin’s disease tissues (lymph nodes) both in the nucleus and cytoplasm. All tissues tested for the presence of Newcastle diesease virus (NDV, an avian paramyxovirus) antigens were negative. Control tissues were obtained from patients with non-Hodgkin’s lymphomas, breast cancers, adenocarcinomas and a number of other disease processes. In control tissues mumps antigens were detected in seven out of 31 specimens and measles antigens in nine out of 18 tissues.