Background This project arises from the lack of information about the reality of the sexual male workers in the city of Lisbon and from HIV/AIDS and other IST prevention projects, adapted to this target audience.

Methods Participating in the project 129 male sex workers, with an average age of 28.32 years (SD = 5,860). Most are single (81.4%) and 48.8% identify themselves as homosexual or bisexual (35.7%). 60.5% have a versatile role in sex, while 36.4% claim just be active. Instruments used to conduct this study: the socio-demographic questionnaire and the Questionnaire of Knowledge on HIV/AIDS which consists of 17 multiple-choice questions (yes, no, I don’t know). This data was collected through an outreach strategy, with a field team operating with the audience, addressing the indoor sex work.

Results Male sex workers present high level of knowledge on HIV/AIDS (average = 14.92, SD = 2.47, range 0 a 17), however, have low levels of optimism (average = 20.89, SD = 4.53, range 12–48) and high levels of self-efficacy in condom use (average = 61.40, SD = 6.29, range 13–65). The correlation analysis shows that higher levels of optimism were negatively associated with self-efficacy (r = –0.203, p = 0.029), indicating a moderate but significant negative relationship: the more optimistic, the less self-efficacy in condom use. Statistically significant differences were found in self-efficacy on condom use and sexual orientation; on nationality and condom use in oral sex and also sex role and self-efficacy in condom use.

Conclusions This Project has been of the utmost importance in preventing HIV/AIDS and other STI, by regular monitoring and routing of the target audience based on felt needs. The distribution of prevention-material and the relationship established with the audience points in that direction. It´s extremely important for the prevention of HIV/AIDS and other STIs among sex workers, work with cognitive and behavioural variables, such as optimism and self-efficacy in condom use.