A step-by-step analysis of Beck's and Hamilton's rating scales showed that both scales failed to differentiate adequately between moderate and severe depression measured by a global clinical assessment. Each item of the scales was tested for calibration, ascending monotonicity, and dispersion parallel to the clinical assessment. Twelve items of Beck's scale and six items of Hamilton's scale were found valid with respect to these criteria. Those items should be taken into account in future research for baseline ratings and for change ratings of depressive states quantitatively.