The Hamilton Anxiety Rating Scale (HARS) is the most widely used semistructured assessment scale in treatment outcome studies of anxiety. Interrater reliability coefficients for the HARS have been previously reported. However, differences in the way clinicians assess symptom severity may reduce reliability. A structured interview guide--The Hamilton Anxiety Rating Scale Interview Guide (HARS-IG)--was developed to standardize clinical probe questions and to minimize interrater variance. Joint-interview and test-retest methods of interrater reliability assessment were used in a group of 30 inpatients. Intraclass coefficient calculations revealed improved interrater agreement with the HARS-IG versus the HARS. The findings of this study demonstrate that the HARS-IG is a more reliable assessment instrument than the semistructured HARS and that it meets established standards of reliability assessment.