OBJECTIVE: As the world population ages with an improved quality of life and sexual longevity, the prevalence of AIDS is rising among the elderly. The purpose of this study was to estimate the vulnerability to AIDS among individuals attending senior community centers in Campo Grande, Mato Grosso do Sul, Brazil. METHOD: This descriptive, exploratory investigation included 329 subjects selected in a probabilistic manner. Individuals with scores on the Mini-Mental State Examination indicating cognitive impairment were excluded from the analyses. Barthel's and Lawton's functional assessment scales were applied. Interviews were conducted to evaluate the presence of cognitive and behavioral factors associated with HIV transmission. RESULTS: Most subjects were non-dependent, fell within the 60- to 69-year age bracket and were female. A majority of individuals reported having knowledge about AIDS and were aware that the elderly are vulnerable to the disease. More than a quarter (26.9%) of the sample reported previous HIV testing. No participants reported drug use, homosexual orientation, or alcohol abuse. A minority of participants reported using medication for erectile dysfunction. Casual and multiple partners accounted for 12% and 34% of reported intercourse experiences, respectively. Condom use was reported by 14% of respondents. CONCLUSION: Unprotected sex was the primary factor accounting for vulnerability to AIDS among the elderly.