A continuing problem in the care of patients suffering with depression is the assessment of how depressed the patient is, and how the level of depression changes over time. In clinical practice the patient is used as his own control, but the psychiatric assessment often has to be made in ways prone to the errors of subjective assessment. The psychiatrist is interested in how the depressed patient views himself and the world around him, that is, in terms of Kelly Personal Construct Theory, what constructs the patient uses to structure areas of his life and where on these constructs the patient sees himself. Personal Construct Theory and the Repertory Grid Techniques provide a useful framework for idiographic estimates of change.