The human cytomegalovirus (HCMV) was first isolated in cell cultures from the oropharynx, which is thought to be a site of primary infection. Although HCMV can be recovered from the oropharynx during reactivation phases, its exact site of latency is not known. In the present study we demonstrated evidence suggesting the presence of latent HCMV in this anatomic region--in the palatine tonsils. Samples from 30 tonsils obtained by tonsillectomy were screened for the presence of HCMV. Out of the 30 tonsil donors, 23 were seropositive for HCMV. Three methods were used in attempts to demonstrate HCMV's presence in the tonsils: (1) viral isolation attempts on various cell cultures, (2) immunohistochemical staining--immunoperoxidase method--designed to detect viral antigens, and (3) DNA dot hybridization with a HCMV-DNA probe designed to detect viral DNA. Neither infectious HCMV nor other viruses were isolated in cell cultures. No viral antigens were detected by immunoperoxidase staining in the tonsillar tissue. Four out of the 30 tonsils studied were found to contain viral DNA. In one case in which the tonsillar mononuclear (MN) fraction was separated from the polymorphonuclear (PMN) fraction, only the first fraction contained the viral DNA.