Calcium channel antagonists selectively block intracerebral vasoconstriction and appear clinically effective in the treatment of migraine. The in vitromethod described in the present report measured both the absolute and relative potencies of a group of calcium blockers. The dihydropyridine drugs, nimodipine and nifedipine, were both the most potent and selective of the calcium antagonists studied. Cinnarizine and flunarizine were essentially equipotent in both basliar and femoral arteries while the traditional therapeutic agents, cyproheptadine and amitriptyline, were 10-fold more potent in femoral than basilar artery. This rapid in vitromethod may provide pharmacologic information which can be used as a guide in the selection of calcium channel antagonists for future clinical trials.