A limited amount of research has been conducted on the psychometric properties of commonly used measures of anxious or depressive symptomatology for use on the internet, although such measures are seeing increasing use in internet administration for both clinical and research uses. A plethora of advantages exist for the use of internet administration of questionnaires, both in terms of assessment and the potential use in treatment monitoring as well as for research. The aim of this study was to examine the psychometric properties of two common clinical measures, the Penn State Worry Questionnaire and the. Depression, Anxiety, and Stress Scale, in an internet administered format (N = 1138). Results suggest that these two measures may be used with confidence in an online format in terms of reliability and validity.