In a first experiment, subjects verbalizing the stream of consciousness for a 5-min period were asked to try not to think of a white bear, but to ring a bell in case they did. As indicated both by mentions and by bell rings, they were unable to suppress the thought as instructed. On being asked after this suppression task to think about the white bear for a 5-min period, these subjects showed significantly more tokens of thought about the bear than did subjects who were asked to think about a white bear from the outset. These observations suggest that attempted thought suppression has paradoxical effects as a self-control strategy, perhaps even producing the very obsession or preoccupation that it is directed against. A second experiment replicated these findings and showed that subjects given a specific thought to use as a distracter during suppression were less likely to exhibit later preoccupation with the thought to be suppressed.