--Despite the current active HIV test policy, the effects of the former policy are still visible, i.e. a relatively low number of individuals that have ever been tested for HIV. --The number of HIV tests and knowledge of current HIV status has increased among visitors to the STI clinic in Amsterdam. --Nevertheless, anonymous HIV surveillance among visitors to the STI clinic shows that a considerable proportion of HIV-infected individuals (24% of men who have sex with men (MSM) and 80% of heterosexuals) are unaware of the infection. --A new opting-out strategy for HIV testing in STI clinics is recommended. --The opting-out strategy may also be applicable to other medical settings, especially those that treat target populations such as MSM, heterosexuals with STI-related symptoms, and persons originating from AIDS-endemic regions. --The opting-out system was initiated in the Amsterdam STI clinic in 2007 in order to further reduce the number of undiagnosed HIV infections.