The levels of Prostacyclin (PGI2 ) and Thromboxane A2 (TXA2 ) were assayed simultaneously (RIA) in the plasma and saliva of 9 patients suffering from classical migraine attacks. The assays were done during an attack-free period. In relation to the control group we observed a significant decrease in the plasma levels of PGI2 together with a sharp increase in TXA2 in saliva. When the patients were treated with nicardipine, a calcium antagonist, the TXA2 increase in saliva did not occur. These results suggest both a systemic and local effect in the classical migraine attacks. We explain and discuss our results by referring to the PGI2 : TXA2 equilibrium system. Nicardipine action might be related to its ability to reduce the calcium entry into the cell induced by thromboxane.