The nature of test anxiety and its relationships to performance and cognitive interference are analyzed from the standpoint of attentional processes. A new instrument to assess dimensions of reactions to tests is presented, and its psychometric properties are described. The scales of the Reactions to Tests questionnaire (Worry, Tension, Test-Irrelevant Thinking, Bodily Symptoms) were compared with regard to intellective performance and cognitive interference. The results were consistent with the idea that the problem of anxiety is, to a significant extent, a problem of intrusive thoughts that interfere with task-focused thinking. In the last of the three studies reported, it was shown that self- preoccupying intrusive thinking can be reduced by means of a task-focusing experimental condition. The studies suggest that the Reactions to Tests questionnaire may be useful in defining anxiety more sharply and improving understanding of how it relates to performance.