AIDS stigmas create significant barriers to HIV prevention, testing, and care and can become internalized by people living with HIV/AIDS. We developed a psychometric scale to measure internalized AIDS-related stigmas among people infected with HIV. Items were adapted from a psychometrically sound test of AIDS-related stigmas in the general population. Six items reflecting self-defacing beliefs and negative perceptions of people living with HIV/AIDS were responded to dichotomously, Agree/Disagree. Data collected from people living with HIV/AIDS in Cape Town South Africa (n=1068), Swaziland (n=1090), and Atlanta US (n=239) showed that the internalized AIDS Stigma Scale was internally consistent (overall alpha coefficient=0.75) and time stable (r=0.53). We also found evidence in support of the scale's convergent, discriminant, and criterion-related validity. The Internalized AIDS-Related Stigma Scale appears reliable and valid and may be useful for research and evaluation with HIV-positive populations across southern African and North American cultures.