Urinary 3-methoxy-4-hydroxyphenethylene glycol (MHPG) excretion, which is thought to reflect CNS norepinephrine metabolism, has been shown to be significantly decreased in some depressed patients. Although there is consensus that urinary MHPG excretion varies directly with mood in rapidly cycling bipolar patients, there is little information on longer term state changes, such as those that accompany recovery from depression. Ten female patients with diagnoses of primary affective disorder were studied initially during an inpatient hospitalization and restudied at least ten months after discharge. Five healthy female comparison subjects were also studied over a similar interval of time. During the baseline period, the patient sample excreted less MHPG than did the comparison group. Improvement in clinical state from a seriously depressed baseline was associated with a significant increase in MHPG excretion, while the patients with recurrences of depression showed no change and continued to excrete less MHPG than the comparison subjects. These results suggest that urinary MHPG excretion may represent an index of psychobiological state in depressive patients.