• Twenty-four-hour urinary excretion rates of norepinephrine, normetanephrine, 3-methoxy-4-hydroxyphenylglycol, and vanillylmandelic acid were repeatedly measured in 12 depressed patients. High (>.83) positive correlations were found between the excretion rates of these four substances. Based on these findings, the conclusion was reached that in depressed patients the 24-hour urinary excretion rates of norepinephrine and any of its three major metabolites reflect total norepinephrine production in the body.