This column explains how a clinician can use an analog scale (1) to elucidate the course of major depressive disorder in a specific patient and (2) to assess response to treatment. This scale complements other standardized rating scales, such as the Montgomery-Asberg Depression Rating Scale (MADRS), because its anchors are tailored to each specific patient in terms of his or her worst depressive episode (ie, episode rated a 10) and how it has responded to treatment in the past, including whether the patient ever has achieved a full remission (ie, score of 0) following the initial onset of the disorder. The scale can then be used to assess how the patient in an acute or chronic active episode responds to new treatment, whether somatic and/or psychotherapeutic, and how that compares to historical responses to previous treatments. Going forward the scale can be used to assess the course of the patient's illness (eg, episodic with full recovery or chronic with more severe episodes and increasing residual symptoms.) Through the use of this analog scale, the patient also develops a better understanding of his or her illness, including how episodes develop and resolve and whether there are factors (eg, interpersonal relationships) that either aggravate and/or are aggravated by the disorder. This simple scale, thus, fulfills many purposes, including history gathering, monitoring the usefulness of different treatment interventions, and patient education.