In an attempt to regulate disappointments people may sometimes change their perceptions of the events leading to an undesirable outcome so that in retrospect this outcome seems almost inevitable. This retroactive pessimism effect was demonstrated in three studies. In the first, sports fans rated the likelihood of success for their team and its opponent before and after an important soccer match. Evidence for significant pre- and post-game probability shifts was found for the fans of the defeated team but not for the supporters of the winning opponent. In the second and the third experiments participants responded to a scenario depicting a loss of stipend that was either large or small in value. Participants were expected to show more evidence of retroactive pessimism with greater disappointment. Indeed, estimates of the probability of a more favorable counterfactual outcome were sensitive to the magnitude of the loss with lower estimates of the probability that things could have turned out better in the large stipend condition. The effect was attenuated, however, when the loss was not personal but rather that of a friend (Experiment 2), or when the disappointment was mitigated (Experiment 3). Copyright © 2002 John Wiley & Sons, Ltd.