Quitting smoking is easy…I've done it many times. This is an old joke, often attributed to Mark Twain, although there seems to be no evidence that he actually ever said it. Nevertheless, like other effective behavior, the joke worked in the past, and there is a good chance it will work well into the future. The reason the joke works is that even nonscientists can relate to what it conveys about the difficulty of maintaining longterm behavior change-previously eliminated behavior tends to return. Scientifically, it has become quite clear that behavior suppressed by a variety of means (e.g., extinction, punishment, omission contingencies, alternative reinforcement, various combinations of these) tends to recur following a wide range of changes in circumstances. Such recurrence goes by different names depending on the specific changes in circumstance that provoke it (e.g., resurgence, renewal, reinstatement, spontaneous recovery), all of which comprise an area of research that is often referred to more generically by the moniker "relapse."Numerous histories/reviews of the remarkably long study of different relapse-like phenomena across different eras and various research domains can be found elsewhere (e.g.