We report on 10 patients suffering from two types of primary headache, migraine and cluster, diagnosed according to IHS criteria, and selected from headache patients attending two Italian headache centers. We briefly review the literature on coexisting migraine and cluster headache, considering the time relationships between these two headaches. The present series seems not to confirm the hypothesis that migraine transforms into cluster headache since both headaches persist together in the patients. The series is of clinical interest particularly with regard to diagnosis and to treatment strategies. Furthermore, while migraine and cluster headache comorbidity must be confirmed by population-based epidemiological studies, the possibility arises that the two conditions may be linked pathophysiologically: common genetic factors or functional alterations in the same central neurological circuits may play a role in the pathogenesis of both disorders.