To the Editor.
—During the past several years, there has been an increasing interest in the clinical use of the dexamethasone suppression test (DST). Although the ultimate clinical value of the DST is far from clear information pointing to to its potential clinical application has been accumulating rapidly. In particular, the article by Carroll and associates1 has further increased this interest. With the added publicity of the mass media, it is not unusual for psychiatrists in large institutions to receive telephone calls from outside psychiatrists and non-psychiatric physicians asking for procedures and interpretations of the DST. From that experience, I wish to make several statements of caution in regard to the clinical application of DST.1. As far as can be ascertained, what Carroll et al called "plasma cortisol" concentration, measured by competitive protein-binding assay,2 is in reality plasma