This study described baseline sociodemographic and oral health characteristics of a subset of HIV sero-positive and sero-negative women who participated in the oral health component of the Women's Interagency HIV Study (WIHS). In 1995-96, 584 HIV sero-positive and 151 sero-negative women from five WIHS core sites were enrolled in the oral study. Data on oral mucosa, salivary glands, dentition and periodontium, along with demographics, socioeconomics, and behavioral characteristics, were used to characterize this population. Mean (SD) age was 37 (8) years for HIV sero-positive and 36 (8) years for sero-negative women; 27% of sero-positive women had CD4 counts < or =200 and 34% had viral loads >50,000 copies/ml. Sero-positive and sero-negative women were similar demographically, as well as on plaque index, gingival bleeding, linear gingival banding, and numbers of DMF teeth and surfaces, but sero-positive women had more abnormal gingival papilla (P = 0.004) and fewer teeth (P = 0.01). Among sero-positive women, those with <200 CD4 counts had more DMF teeth (P = 0.007), and the number of DMF surfaces increased with decreasing CD4 counts (P = 0.04). Sero-positive women who fit the Center for Disease Control (CDC) AIDS criteria were also more likely to have more DMF teeth (P = 0.004), DMF surfaces (P = 0.003), and decayed and/or filled (DF) root surfaces (P = 0.0002) compared to sero-positive women without AIDS. Dental and periodontal variables showed little difference between HIV sero-positive and sero-negative women. Among sero-positive women, there were significant differences in coronal and root caries by AIDS diagnostic criteria, but no periodontal indicators by either AIDS diagnostic criteria or CD4 status, were observed.