Abstract Possible factors capable of inducing spasm of the larger muscular arteries have been searched for by recording the dorsalis pedis pulses bilaterally in the anesthetized dog, employing the pulse in the left leg as a control while various stimuli were applied to the right leg. Direct trauma or various forms of reflex stimulation failed to elicit any significant change in the pulse. Definite pulse changes were observed, however, with direct motor nerve stimulation. Maximal responses recorded from the experimental side with sciatic nerve stimulation were accompanied by a 75 per cent reduction in pulse pressure and a 20 per cent reduction in mean pressure, associated with a 50 per cent decrease in blood flow through the leg. The possible bearing of these observations upon large artery spasm observed clinically is discussed.