The dexamethasone suppression test (DST) has been primarily investigated as an aid in diagnosing endogenous depression; yet, its major clinical use has been as a predictor of treatment response. It is commonly held that 1) an abnormal DST predicts response to somatic (and not psychologic) therapies, 2) an abnormal DST predicts response to noradrenergic antidepressants, and 3) a normal DST predicts response to serotonergic agents. The DST predicted response to somatic therapies in only 6 of 16 published studies. No single methodologic factor, such as population variables, DST technique, or study design, can explain the marked discrepancy in study results. Only two of seven studies examining the DST and response to neurotransmitter-specific antidepressant groups found a positive relationship. The evidence that the DST predicts response to noradrenergic agents is weak. The DST does not predict acute response to somatic treatment in general or response to specific antidepressants. The selection of the appropriate treatment for depressed patients is still best made using clinical criteria.