• Serum dopamine-β-hydroxylase (DBH) activity was measured during headache-free intervals in 17 patients with migraine and during the headache interval in 16 patients with muscle contraction headache, as well as in 40 normal subjects. The DBH activity was significantly higher in the migraine patients (46.5 ± 4.5 units) than in the controls (24.9 ± 2.4 units), whereas no significant difference was observed between the patients with muscle contraction headache (29.4 ± 4.5 units) and the controls.