The subgingival microflora of 39 HIV + subjects with gingivitis or adult Periodontitis was cultured quantitatively anaerobically for bacteria, spirochetes, and mycoplasma and aerobically for yeasts. Isolates were characterized by conventional biochemical tests, Polyacrylamide gel electrophoresis of soluble proteins, cellular fatty acid profiles, immunofluorescence, and immunodiffusion. In general, the same types of bacteria were isolated from the subgingival crevice of HIV + subjects as we previously had isolated from the subgingival crevice of non‐HIV subjects. A statistically significant difference was found between the composition of the flora of HIV + subjects with adult Periodontitis (AP) and concurrent studies of a non‐HIV + AP population.Mycoplasma salivariumwas significantly elevated in the HIV+ subjects examined. Yeasts were isolated from only 10% of the samples and from 13% of the HIV‐positive subjects at 0.05 to 0.0002% of the total cultivable count when present.J Periodontol 1993; 64:48–56.