Although clinically distinctive types of periodontal disease are known to be associated with HIV infection, the pathogenesis remains unclear. In the present study, the subgingival microflora of 21 HIV-infected and 11 HIV-free ethnic Chinese were studied using the direct microscopic and anaerobic culture methods. Motile curved rods were found to be three times higher in the HIV-infected group under direct microscopy. Otherwise, there were no significant differences between the diseased and healthy groups when analyzed either in relation to the morphotype distribution or Gram stain morphology or oxygen tolerance. The most common bacteria isolated were Capnocytophaga species followed by Prevotella loescheii, Streptococcus sanguinis, Lactobacillus spp. and Fusobacterium spp. Although there were 20 bacterial species that were strictly limited to the HIV-infected group, and 5 limited to the healthy group, none of the species was a predominant isolate in either group (p>0.05). These findings agree with previous studies which report that subgingival bacteria of HIV-infected individuals (with or without periodontal disease) are similar to those found in healthy HIV-free individuals (with or without periodontal disease). Further work examining the subgingival microflora from patients with specific and/or severe forms of HIV-associated periodontal disease is required to shed light on the pathogenesis of this complex clinical entity.