This study evaluated the 1994, 1995 and 1996 Dutch safer sex campaigns as to their effectiveness in terms of improved attitudes, perceived social norms, self-efficacy and intentions regarding safer sex. The hypotheses were tested that variables become more positive when campaigns are conducted and less positive when campaigns are discontinued. A comprehensive design, including a baseline-post-test/post-test-only group design and a longitudinal or multiple assessment group design, was employed to exclude testing effects, history effects, cultural changes and sample differences as alternative explanations. The results show that despite high baseline levels, the campaigns positively affected all variables. Importantly, levels of all variables decreased when no campaign was conducted. It is concluded that campaigns are needed to maintain high levels of determinants of safer sex and that future campaign goals should be formulated in terms of stabilization instead of growth.