The evidence which suggests that urinary 3-methoxy-4-hydroxyphenethylene
glycol (MHPG) may reflect the disposition of norepinephrine (NE) within the brain is
briefly reviewed, and studies from different research groups indicating that some depressed
patients excrete less than normal quantities of MHPG are noted. Data which indicates that
those depressed patients who excrete less than normal amounts of MHPG can be identified
by explicit clinical criteria as well as by a favorable treatment response to imipramine are
summarized. These findings, as well as others which are noted in this paper, lead us to
conclude that there is an identifiable group of depressed patients who have a disorder of NE
metabolism and/or disposition which is integral to the illness per se.