Pupillography before and after Cocaine eye drops was performed in twenty patients subject to vascular headaches. 65% had anisocoria which after Cocaine eye drops increased to 90%. The smaller pupil was not necessarily on the hemicrania side. Lid droop was observed in nine patients. In ten, the eyelid droop persisted after Cocaine eye drops. The pupil size was not significantly smaller than in a normal group and it was round in all but two cases. These findings suggest that patients with cluster and migraine headache have a subtle chronic sympathetic deficiency which affects both the pupil and eyelid. This deficiency may increase during the acute phase, at times causing a prominent Horner Syndrome. Adrenaline deficiency is locally responsible for these changes. No significant changes were found between cluster and vascular headache patients in this small sample. Pupillography and sympathomimetic eye drops are objective tests in the diagnosis of vascular headache in clinically difficult cases; they are a painless expedient procedure.