Patients with migraine who believed that red wine but not alcohol in general had a headache-provoking effect on them were challenged either with red wine or with a vodka and diluent mixture of equivalent alcohol content, both consumed cold out of dark bottles to disguise colour and flavour. The red wine, which had a negligible tyramine content, provoked a typical migraine attack in 9 of 11 such patients, whereas none of the 8 challenged with vodka had an attack. Neither red wine nor vodka provoked such episodes in other migrainous subjects or controls. These findings show that red wine contains a migraine-provoking agent that is neither alcohol nor tyramine.