Nitroglycerin administration provokes spontaneous-like migraine attacks in migraine and cluster headache (CH) patients. Nitroglycerin-induced migraine-like headache has been used as an experimental model of migraine. In this paper, we evaluate the possibility of using the nitroglycerin provocative test (NPT) as a supportive measure in the diagnosis of primary neurovascular headaches by assessing its reliability on a large population and adopting strict criteria for rating the response as positive or negative. Our population consisted of 197 migraineurs, 42 subjects suffering from cluster headache and 53 healthy controls. In migraine without aura, the test sensitivity was 82.1%, specificity 96.2% and accuracy 85.5%, while in subjects suffering from migraine with aura, the reliability of the NPT was less satisfactory (sensitivity 13.6%, specificity 96.2% and accuracy 72%). In CH patients tested during the active phase of the disease the sensitivity was 80.6%, specificity 100% and accuracy 92.9%. NPT is an easy, low-cost and reliable method for supporting the diagnosis of migraine without aura and cluster headache.