Prevention campaigns and new antiretroviral therapies caused a decline in HIV-infections as well as mortality from HIV/AIDS in industrialised countries. Despite this development AIDS is one of the ten mean causes of death worldwide, with 3,1 million deaths in 2002. Hence there is an urgent need for prevention and information campaigns, which ideally should start in early childhood or at school age. It is well known that preventive strategies start at a time when the risk or the possibility of a risky behaviour does not yet exist. A WHO-report in 1993 showed, that sex education often comes too late, as sexual activity of adolescents is already on its way. Persons who are already sexually active can be influenced to have fewer sexual partners and to increase safer sex methods. There is no evidence for causing a higher risk by sex education of adolescents. In Austrian schools numerous experts and organisations cooperate in the sphere of sex education and STD-prevention. School children in Vienna are confronted with this topic by the schools they attend according to the Sex Education-Act of 1970 on a voluntary basis. Various examples of effective teaching models prove intensive efforts and successful interdisciplinary cooperation. This study analyses common risk-reduction-methods and describes the Austrian way of HIV/AIDS/STD prevention in school children, although there is no obligation for sex education in schools, according to the School Teaching-Act of 1986, which leads to better knowledge and subsequent risk behaviour of adolescents in the same geographical area.