A migraine attack is a multiphasic event. In some patients the initial phase of the attack is characterized by the presence of "prodromes" or "premonitory symptoms" which are not recognized by the patient as part of the attack. Premonitory symptoms are defined as "symptoms preceding and forewarning of a migraine attack by 2-48 hours, occurring before the aura in migraine with aura and before the onset of pain in migraine without aura". Migraine premonitory symptoms should be differentiated from aura and symptoms of premenstrual syndrome. This differentiation, which is crucial to correct diagnosis, is based on two principal aspects, namely, the timing of these premonitory symptoms prior to the headache pain and their clinical characteristics. The neurotransmitters dopamine and serotonin are possibly involved in the development of premonitory symptoms, as demonstrated by experimental models and by the efficacy of migraine aborting and preventive treatments. Accurate recording of premonitory symptoms may contribute to efforts to design the best therapeutic approach in migraine patients.