Recent research has shown that magnesium levels in serum, salivary secretions and red blood cells are reduced in migraine patients with and without aura, both ictally and interictally. This suggests that lower magnesium levels can contribute to the etiopathogenetic mechanisms underlying migraine attacks. It has been suggested that mononuclear magnesium content is a reliable index of magnesium nutritional status, as it is more closely related to the total body stores than other biochemical indices. Therefore we determined mononuclear magnesium content in adult migraine patients with and without aura, in headache-free periods and, in a number of patients, during attacks. Migraine patients with and without aura, assessed in interictal periods, had a reduced mononuclear magnesium content compared to age-matched healthy control subjects. No significant variations were observed between ictal and interictal periods in migraine patients with aura and without aura. The lower magnesium content in mononuclear cells could indirectly indicate the reduction of brain magnesium concentration, which has recently been demonstrated in the course of migraine.