The placebo effect is an apparent improvement in someones health/behavior that is not due to an active substance but rather to someones belief or expectation that (s)he will improve. Research on placebo effects is scarce, because placebos cannot be ?patented? or commercialized. Placebos are often cast as the villains to beat in medical research, although the placebo effect is a phenomenon that could guide us toward a better understanding of health/behavioral improvements. By conducting a series of longitudinal laboratory experiments, I aim to investigate to what extent placebo effects are enduring rather than transient phenomena. On the one hand, it could be expected that experiencing a placebo effect attenuates the strength of subsequent placebo effects. On the other hand, (un)favorable experiences could sustain or even amplify expectancies in subsequent experiences. Direct experience with a placebo could therefore attenuate but also amplify subsequent placebo effects. In addition to documenting the persistence of placebo effects, this research aims to outline which factors moderate the longitudinal effects of placebo effects. Depending on the ambiguity of the experience, expectancies may be updated over time by post-experience information. This research will yield significant theoretical contributions, not only for marketing academics, but for fundamental research in psychology and medicine as well. Moreover, this research project will yield important practical insights for public policy makers, marketing practitioners, drug developers and citizens alike.