TO THE EDITOR: Indeed, the ambiguous application of the terms "agitation" and "retardation" was a primary impetus for the preparation of our article. At various times the terms have been used in the literature, and in our diagnostic criteria, to indicate any internal or external manifestation of slowness or restlessness during an episode of depression. Perhaps as a result, the likely source of these phenomena, and thus their meaning and significance, has been obscured. We intentionally focused this article on studies of objectively quantifiable aspects of motor change in depression. Using this approach, we examined evidence suggesting links between these observable motor symptoms and the possible pathophysiological basis of some depressions. Understanding the subjective experience of slowness or agitation is important for different reasons, most significantly for patient care. The findings of Dr. Lemke and associates suggest that the association between the subjective experience and objective assessment of agitation and retardation is complex, and a positive correlation should not be assumed. This will be a useful and intriguing area for further investigation.