A review of periodontal disease as a manifestation of HIV infection suggests a shift in emphasis over the past 5 years. Initially the focus was on newly described forms of periodontal disease (i.e., HIV-associated gingivitis or linear gingival erythema (LGE); HIV-associated periodontitis or necrotizing ulcerative periodontitis (NUP). While the clinical definition of LGE varies from study to study, an association between LGE and Candida infection has been described. Furthermore, the prevalence of NUP is quite low and this disorder is associated with severe immunosuppression. In contrast, the focus today is on the accelerated rate of chronic adult periodontitis occurring in seropositive patients. While the organisms that characterize adult periodontitis in seronegative individuals are present in subgingival plaque from seropositive individuals, reports suggest that atypical pathogens are also present (i.e., Mycoplasma salivarium, Enterobacter cloacae). Recent studies from our laboratory have identified a novel strain of Clostridium isolated from the subgingival plaque of injecting drug users that has pathologic potential. This organism, however, was found in both seropositive and seronegative individuals in this cohort, suggesting an association with lifestyle rather than serostatus. In addition, data has been published examining the local host response in periodontitis in seropositive individuals. Distinctly elevated levels of IgG in gingival crevicular fluid (GCF) have been observed in seropositive patients. Furthermore, data from our laboratory examining inflammatory mediators in GCF (polymorphonuclear leukocyte lysosomal enzyme beta-glucuronidase and the pro-inflammatory cytokine interleukin-1 beta) suggests an altered response in patients with HIV infection. The alteration manifests as the absence of the expected strong correlation between polymorphonuclear leukocyte activity in the gingival crevice and clinical measures of existing periodontal disease, as well as elevated levels of interleukin-1 beta in sites with deeper probing depths. Therefore, it can be concluded that the progression of periodontal disease in the presence of HIV infection is dependent upon the immunologic competency of the host as well as the local inflammatory response to typical and atypical subgingival microorganisms.