This article discusses the social representations of women living in common-law marriage in terms of their vulnerability to becoming infected with HIV/AIDS. Data were obtained through the free association of words, and consisted of an excerpt of a study founded on the Social Representations Theory developed with HIV-negative women living in the state capital and cities in the interior of Bahia. The correspondence factor analysis showed significance for the variables: origin, education level and time spent in common-law marriage. Their acceptance of marital affairs emerged as a vulnerability factor for respondents with one to five years spent in common-law marriage, living in cities in the interior. Women from the capital, with 6-10 years spent in common-law marriage, reported monogamy as a form of prevention. Women with a longer common-law marriage who had completed only a primary education reported feeling invulnerable, which was the opposite of those with one to five years in common-law marriage with a secondary education. Results show there is a need for more interventions aiming to denaturalize the socio-cultural coercions that generate representations and make women in common-law marriages more vulnerable to AIDS.