The effect of l‐norepinephrine (NE) infusion on the digital circulation was studied in four groups of patients: normotensive subjects prepared by indirect heating supplemented by (a) intravenous 2,6‐dimethyl,‐1‐diethyl piperidinium bromide (SC‐1950) or (b) by intravenous trimethaphan camphorsulfonate (TMCS); and hypertensive subjects prepared in the same way, the supplementing drug again being either (c) SC‐1950 or (d) TMCS. Less NE was required in the normotensive groups to produce a given degree of vasoconstriction when TMCS was the supplementing drug. The same effect was probably true of the hypertensive groups although this could not be demonstrated statistically from these data. This effect of TMCS cannot be satisfactorily accounted for by the liberation of histamine or by more efficient vasodilatation but is probably attributable to direct peripheral blockade by the drug of the entrance of NE into neural stores.