&NA;We performed in vitro experiments with a small volume chamber to determine the inhibitory effect of nifedipine on serotonin‐, phenylephrine‐, and potassium‐induced contractions of canine basilar and femoral arteries. Nifedipine, an inhibitor of the influx of extracellular calcium into smooth muscle cells, was found to be a sensitive inhibitor of contractions of the basilar artery induced by all three agents. In contrast, nifedipine did not significantly inhibit the serotonin‐ and phenylephrine‐induced contractions of the femoral artery but did inhibit potassium‐induced contractions of the femoral artery. Calcium‐induced contractions of the basilar artery were also inhibited by nifedipine. These experiments demonstrate a relatively selective effect of nifedipine on the basilar artery, and a mechanism to explain this selective effect is postulated.