Even though viruses have been implicated in the etiology of several medical and dental disorders, little or no data are available on the possible involvement of human viruses in the pathogenesis of human periodontal disease. This study investigated the presence of human cytomegalovirus, Epstein-Barr virus, herpes simplex virus, human papillomavirus and human immunodeficiency virus (HIV) in crevicular fluid samples from 30 patients with advanced periodontitis and 26 subjects with gingivitis. Viral identification was performed on direct subgingival samples from 3 diseased sites in each patient using the polymerase chain reaction technique. Seventy-eight percent of advanced periodontitis patients were positive for at least one of the five test viruses. Cytomegalovirus was detected in 60% of the periodontitis patients, Epstein-Barr virus in 30%, herpes simplex virus in 20%, human papillomavirus in 17% and HIV in 7%. Forty percent of the periodontitis patients revealed coinfection by 2 to 5 viruses. Only 31% of the gingivitis subjects showed a positive viral identification in crevicular fluid, and infected individuals only revealed human cytomegalovirus. This study demonstrated that human viruses may occur in periodontitis lesions with relatively high prevalence. The pathogenetic significance of human viruses in destructive periodontal disease needs to be determined.