It has been well-characterized that administration of GTN to migraine patients induces an immediate headache which is of short duration, bilateral and throbbing. This is followed, up to 5 hours later, by a delayed headache that has features of a migraineur’s spontaneous attacks. Although the immediate headache is generally also reported in non-migraineurs, the delayed headache is rarely observed. Despite GTN being used to provoke headache there is little literature available looking at the reproducibility of the delayed GTN-induced headache or whether this headache responds to treatment. Induction of GTN delayed headache in migraine patients may provide the basis for a model to test novel anti-migraine drugs for signals of putative efficacy.