Development and validation of the Penn State Worry Questionnaire. Behaviour Research and Therapy, 28, 487-495.] for weekly assessment of worry was evaluated in a brief treatment study. Cognitive restructuring techniques were taught to 28 nonclinical high-worriers, 14 of whom served as a control group in a lagged waiting-list design. Results showed that the Penn State Worry Questionnaire-Past Week (PSWQ-PW) was highly reliable and substantially valid in the assessment of both (a) weekly status of worry and (b) treatment-related changes in worry: average Cronbach's alpha was 0.91; average convergent correlation with a past-week adaptation of the Worry Domains Questionnaire [Tallis, F., Eysenck, M. W. and Mathews, A. (1992). A questionnaire for the measurement of nonpathological worry. Personality and Individual Differences, 13, 161-168.] was 0.63 and pre-post improvement on PSWQ-PW showed a 0.71 correlation with the Questionnaire of Changes in Experiencing and Behavior [Zielke, M. and Kopf-Mehnert, C. (1978). Veränderungsfragebogen des Erlebens und Verhaltens. Weinheim, Germany: Beltz Test Gesellschaft.]. It is concluded that the PSWQ-PW is a useful instrument for monitoring pathological worry in experimental and applied settings.