In order to investigate headache related to intravenous immunoglobulin, we studied a 36-year-old woman with a history of migraine receiving weekly intravenous immunoglobulin for refractory myasthenia gravis who experienced severe headaches with each treatment. Neurological examination, CT scan of the head, and a lumber puncture after the first headache were normal. Significant therapeutic response was based upon 50% reduction in pain and associated features. Headache features included throbbing pain which worsened with head movement and was associated with severe photophobia and nausea. Sumatriptan, 6 mg subcutaneous, reduced headache significantly with resolution of associated complaints. Treatment prior to intravenous immunoglobulin with dihydroergotamine mesylate resulted in development of only a mild dull ache without further development of severe head pain. Dihydroergotamine mesylate was also abortive in the few instances when the headache worsened. Headaches associated with intravenous immunoglobulin may have features of migraine and may be successfully prevented and/or treated with 5-HT1D receptor agonists.