Paroxysmal hemicrania is a rare syndrome characterized by repeated attacks of strictly unilateral, severe, short-lasting pain occurring with cranial autonomic features. The hallmarks of this syndrome are the relatively short attacks and the exquisite response to indometacin. We describe the phenotype of this condition in a series of 31 patients. The mean duration of attack was 17 min. The mean attack frequency was 11. The distribution of the pain was orbital and temporal in 77% of the patients, retro-orbital in 61%, frontal in 55%, occipital in 42%; although pain was also reported in the vertex, second division of trigeminal nerve, neck, nose, jaw, parietal region, ear, teeth, eyebrow, shoulder (ipsilateral and bilateral), arm and third division of trigeminal nerve. Of the cohort, 87% had lacrimation, 68% had conjunctival injection, 58% rhinorrhoea, 54% nasal congestion, ptosis and facial flushing. Other cranial autonomic features include eyelid oedema, forehead/facial sweating, sense of aural fullness and periaural swelling, miosis, mydriasis and swelling of the cheek. The majority of the patients (80%) were agitated or restless, or both, with the pain and 26% were aggressive. All patients had positive placebo control indometacin test (100-200 mg intramuscularly), or a positive oral indometacin trial or both. We suggest the International Headache Society criteria be revised to remove specification of attack site, and to include the full range of cranial autonomic features. Currently, the sine qua non for paroxysmal hemicrania is a response to indometacin. Since there is no reliable clinical marker of that response we recommend an indometacin test, either orally or by injection for any patient with lateralized discrete attacks of head pain with associated cranial autonomic symptoms.