Gay men and lesbian women face health inequities as well as disparate treatment from healthcare providers. Stereotypes surrounding sexual health might contribute to these disparities. In five studies (N = 1858), we explored sexual health stereotypes about gay men and lesbian women and their implications in prejudice/discrimination. In Studies 1, 2A and 2B, we found people explicitly associated gay men with promiscuity and sexually transmitted infections (STIs) more than lesbian women or straight men/women. In implicit association tests, both gay men and lesbian women were more associated with promiscuity and STIs than straight counterparts. Studies 3A and 3B showed that these associations have consequences: people expressed more prejudice and discrimination toward gay men and lesbian women with STIs versus those with non-STIs or straight counterparts with either disease type. Taken together, the current research identifies some psychological factors that may underpin health disparities and healthcare barriers for gay and lesbian people.