Magnesium has a crucial contribution in the pathogenesis of migraine. Low magnesium level has been detected in patients with migraine. The RBC magnesium assay is a good method to assess for deficiency. Aim of the present study is to find the role of magnesium in patients with migraine and to study the correlation between serum and RBC magnesium levels in case and control group. It is a prospective case control study done in 20 healthy volunteers and in 20 patients with migraine diagnosed on the basis of International Headache Society (HIS) criteria. The mean serum and RBC magnesium levels in patients with migraine was found to be significantly lower than that of the control group .The RBC magnesium levels were lower even when the serum magnesium levels were near normal in patients with migraine. Magnesium deficiency is a precipitating factor for migraine and prophylactic administration of magnesium will be an effective option to reduce the frequency of migraine attacks.