The Hamilton Rating Scale for Depression (HAM-D) and the Montgomery-Asberg Depression Rating Scale (MADRS), two widely used depression scales, each have unique advantages and limitations for research. The HAM-D's limited sensitivity and multidimensionality have been criticized, despite the scale's popularity. The MADRS, designed to be sensitive to treatment changes, is briefer and more uniform. A limitation of the MADRS is the lack of a structured interview, which may affect reliability. The HAM-D and the MADRS are often used conjointly as endpoints in depression trials. We designed a hybrid questionnaire that allows administration of MADRS and 31 HAM-D items simultaneously. Seventy mood disorder patients (60 bipolar I, 10 major depressive disorder) were administered the HAM-D/MADRS Interview (HMI) as part of a larger study. Interrater reliability for 50 patients was excellent for the HAM-D and the MADRS (ICC=0.97-0.98). MADRS item reliabilities (ICC=0.86-0.97) were higher than obtained in studies that did not use a structured interview. Reliability coefficients for seven HAM-D(31) 'atypical' symptoms ranged from 0.77 to 0.95. HMI was highly correlated with the Global Clinical Impressions Scale. This is the first study we know of to investigate the reliability of a structured interview of either the MADRS or of the HAM-D(31). The HMI provides an easily administered, reliable method of rating depression severity which may improve consistency and validity of study findings.