This study investigated psychological effects associated with tendencies to focus one's thinking on positive versus negative outcomes of concluded stressful events, called respectively, positive and negative thinking. Four questions were addressed: (a) whether positive and negative thinking benefit or reduce psychological well-being, (b) whether these effects are transitory or enduring, (c) whether they are limited to thoughts about an event's impact on oneself or generalize to thoughts about an event's external consequences, and (d) whether tendencies to think positively or negatively about prior stressors influence psychological vulnerability to the impact of future ones. College students completed an event-outcome appraisal questionnaire designed to make salient positive and negative thoughts about the outcomes of recent stressful events. Subjects' well-being was then assessed both immediately after the salience manipulation and again 8 weeks later. Positive thinking increased the well-being that subjects reported immediately after their thoughts were assessed, but was unrelated to the well-being they reported after an 8-week delay. This suggests that although thinking positively about past event outcomes may temporarily lead to perceptions of increased well-being while the thoughts are salient, it has no enduring influence. In contrast, negative thinking was associated with lower reported well-being not only when the thoughts were salient but after a delay as well. Psychological effects associated with both types of thinking were due mostly to self-relevant thoughts rather than to externally relevant ones. Negative thinking about prior stressor outcomes appeared to increase vulnerability to the impact of later ones on several aspects of well-being. Overall, results for negative thinking are consistent with evidence reported after an 8-week delay. This suggests that although thinking positively effects that persist over time. However, positive thinking does not seem to have beneficial effects that continue once these thoughts are no longer salient.