Platelet function has been postulated as playing a role in the pathogenesis of migraine. This study aimed to investigate to what extent beta 1-selective and non-selective beta-blockers interfere with the platelet function in migraine patients. Twelve patients with classical migraine were included. After a 2-week drug-free period, the patients were randomly allocated to either beta 1-selective metoprolol (50 mg b.i.d.) or non-selective propranolol (40 mg b.i.d.) treatment for one month. After a wash-out period, the patients were changed to the corresponding beta-blocker for one month. ADP-induced platelet aggregability, platelet cAMP, ATP and ADP levels, plasma cAMP and TxB2 concentration, as well as the serum production of TxB2 were measured before and after each treatment period. After propranolol treatment, the patients showed lower ADP threshold values for producing irreversible platelet aggregation and lower platelet and plasma cAMP levels as compared to metoprolol. Neither of the beta-blockers induced any change in the plasma concentration or serum production of TxB2. In conclusion, non-selective beta-blockade (propranolol) significantly increases the platelet aggregability compared to beta 1-selective blockade (metoprolol).