The upper and lower 5% of 456 undergraduate students who completed the Constructive Thinking Inventory (CTI) were subjected to a laboratory stress test. In support of the hypothesis, poor constructive thinkers reacted to the stress with a greater increase in negative thoughts and negative emotions, and exhibited a greater increase in blood pressure and other measures of physiological arousal than did good constructive thinkers. Examination of thought patterns indicated that poor constructive thinkers did not differ from good constructive thinkers in positive thinking, but did differ in some aspects of negative thinking. It was concluded that an increased number of physical symptoms reported by poor constructive thinkers may be mediated by the increased stress produced by their maladaptive thinking style. (Author)