['Viruses from the Herpesviridae family may be implicated in the pathogenesis of periodontal disease. The aim of this investigation was to compare the subgingival frequency of human cytomegalovirus (HCMV) in subjects affected by periodontitis to periodontally healthy subjects and to assess the correlation of HCMV with periodontal clinical parameters and periodontopathic bacteria.', 'Thirty subjects with periodontitis (20 with chronic periodontitis and 10 with aggressive periodontitis) were included in the study. A group of 22 periodontally healthy individuals served as controls. Clinical periodontal parameters of probing depth (PD) and clinical attachment level (CAL) were recorded using a computerized periodontal probe. Subgingival plaque samples were processed for viral identification by nested polymerase chain reaction and bacterial identification by culture. Clinical periodontal parameters, frequency of detection of HCMV, and microbial composition were compared between the groups using the two-tailed Student t, chi(2), and Mann-Whitney tests. Logistic and linear regression analyses were performed to measure the association between virus-bacterial coinfection and clinical parameters (P < or =0.05).', 'HCMV detection was more prevalent (P < or =0.05) in periodontally diseased subjects compared to healthy ones. Furthermore, in all groups, PD and CAL were increased in HCMV-positive sites. In the periodontitis groups, higher frequencies and levels of specific periodontopathic bacteria were detected in HCMV-positive sites.'] Does subgingival human cytomegalovirus correlate with increased clinical periodontal parameters and bacterial coinfection in periodontitis?