The article by Schatzberg et al1 in this issue of the Archives on the "D-score" reflects an unusually impressive and sustained effort. This work was initiated by Dr Joseph Schildkraut2 who is well known for providing one of the earliest formulations of the catecholamine hypothesis of affective disorders. The D-type score was the result of a discriminant function analysis of urinary catecholamine metabolites carried out with a stepwise entry of variables in the order in which they contributed to discriminating between a small group of bipolar manic-depressive and unipolar chronic charactrological depressions. Dr Schildkraut and Schatzberg and colleagues had observed that a single urinary catecholamine metabolite, 3-methoxy-4-hydroxyphenylglycol (MHPG), was by itself present in a significantly lower concentration in the bipolar than unipolar chronic characterological depressions and then considered the important possibility "that the other urinary metabolites might also contain information that would be useful in differentiating these two