With the advent of DSM-III-R, the diagnostic criteria for generalized anxiety disorder (GAD) shifted in emphasis from the autonomic arousal to the cognitive component of the disorder, namely worry. The Penn State Worry Questionnaire was developed to assess the trait of worry and has proven to be a reliable and valid measure in a series of studies largely based on college student samples. The purpose of the present study was to assess the psychometric properties and utility of the PSWQ in a clinical sample of 436 anxiety disorder patients and 32 normal controls. Factor analysis indicated that the PSWQ assesses a unidimensional construct. Furthermore, the PSWQ evidenced quite favorable internal consistency using GAD patients and each of the other anxiety disorder groups and normal controls. The validity of the PSWQ was supported by an analysis indicating that the measure distinguished. GADs from each of the other anxiety disorder groups including those with obsessive-compulsive disorder. Moreover, correlations between the PSWQ and measures of anxiety, depression, and emotional control supported the convergent and discriminant validity of the measure. Collectively, the findings speak favorably to the use of the PSWQ in research examining the nature and treatment of GAD and the processes of normal and pathological worry.