Background Given the shortage of community-based HIV testing initiatives in resource-rich countries not targeting most-at-risk populations, we aimed to evaluate whether a highly visible mobile programme promoting and offering rapid HIV testing in the street can attract persons at risk for infection who have never been tested.

Methods Between 2008 and 2011, the programme served 7552 persons in various Spanish cities who answered a brief questionnaire while awaiting their results. The factors associated with being tested for the first time were analysed using two logistic regression models, one for men who have sex with men (MSM) and the other for only heterosexual men (MSW) and women.

Results 3517 participants (47%) were first-time testers (24% of MSM, 56% of MSW and 60% of women). Among them, 22 undiagnosed HIV infections were detected with a global prevalence of 0.6% and 3.1% in MSM. Undergoing a first HIV test was independently associated with age <30, being from Spain or another developed country, lack of university education, having fewer partners, having had unprotected sex with casual partners and not having been diagnosed with a sexually transmitted infection. In heterosexuals, also with never injected drugs, and in MSM, with not being involved in the gay community. Among those tested for the first time, 22% had never thought of being tested and 62% decided to be tested when they passed by and noticed the programme, regardless of their previous intentions.

Conclusions This community programme attracted a substantial number of persons previously untested and particularly hard to reach, such as those with low education and MSM who were least involved in the gay community. Programme visibility was a decisive factor for almost two of every three persons who had never been tested.