Visceral lesions consistent with either herpes simplex or varicella-zoster infection were recognized at autopsy of 31 patients with cancer. An antemortem diagnosis based on skin lesions was made in ten cases, but more widespread disease was not usually considered. Herpesvirus infection did not appear to be related temporally to the development of leukopenia, hypoalbuminemia, hypogammaglobulinemia, or various forms of therapy, although any of these may have been important factors in a given case. Herpetic infection may predispose to establishment of monilial esophagitis. The evolution of herpetic lesions frequently involved local thrombosis and featured various degrees of hemorrhagic and infarctive necrosis at the sites of infection.