Primary headaches are among the most prevalent neurological disorders, afflicting up to 16% of the adult population. Associated pain originates from intracranial blood vessels that are innervated by sensory nerves storing several neurotransmitters. In primary headaches, there is a clear association between the headache and the release of calcitonin gene-related peptide (CGRP) but not with other neuronal messengers. The specific purpose of this review is to describe CGRP in the human cranial circulation and to elucidate a possible role for a specific antagonist in the treatment of primary headaches. Acute treatment by administration of a triptan (5-HT1B/1D agonist) results in alleviation of the headache and normalization of the elevated CGRP level. The mechanism of action of triptans involves vasoconstriction of intracranial vessels and a presynaptic inhibitory effect of the trigeminal sensory nerves. The central role of CGRP in migraine and cluster headache pathophysiology has led to the search for small molecule CGRP antagonists, which would predictably have less cardiovascular side effects as compared to the triptans. The initial pharmacological profile of such a group of compounds has recently been disclosed. These compounds have high selectivity for human CGRP receptors and are reported to be efficacious in the relief of acute attacks of migraine.