Since 1985 the Swiss Federal Office of Public Health and the Swiss AIDS Foundation are promoting AIDS prevention campaigns. A multimedia information campaign with the main slogan "STOP-AIDS" began in Feb. 1987 and is still under way. Multiplying effects are stimulated. An evaluation program is following continuously these campaigns, examines knowledge, attitude and behaviour changes in several groups of the population and analyses the conditions of these changes. The evaluation shows that the campaign and its objectives reached the general population and the target groups. Noticeable changes in attitudes and behaviors are taking place in the way of better protection in various observed groups, moderately or strongly exposed to HIV infection.