Findings using cordance contrast with those reported in previous QEEG studies of antidepressant medications, performed in depressed as well as normal control subjects. These studies have shown QEEG effects of antidepressant medication, such as decreased theta or alpha band activity, that are not related to changes in clinical state. In particular, normal subjects receiving antidepressant medications have been reported to show changes in conventional QEEG power measurements that may be useful characteristics of antidepressant medication for medication development purposes. Similar changes in QEEG power have been reported in depressed subjects who do not show clinical improvement (Saletu et al 1982, 1983, 1985, 1986, 1987, 1988; Sannita et al 1983, 1990; Itil et al 1984; Herrmann et al., 1991; Luthringer et al., 1996). The relationship of these immediate EEG changes in control subjects to eventual clinical response in a depressed population is unclear. Other QEEG work with depressed subjects has found that changes from baseline in theta power early in the course of treatment may characterize groups of depressed patients who are more likely to respond to antidepressant treatment (Ulrich et al., 1994). Unfortunately, the changes lacked the specificity to allow response prediction for individual subjects, and the physiologic meaning of these changes in theta power is not clear.