Left circumflex coronary blood flow was increased significantly (20 per cent) during stimulation of somatic afferent fibers. The change in CBF was associated with significant increases in heart rate and arterial pressure and significant decrease in coronary vascular resistance. Controlling heart rate or preventing cardiac beta-adrenergic effects with propranolol during somatic nerve stimulation resulted in increases in CBF and arterial pressure with no change in coronary resistance. These results indicate that stimulation of a somatic nerve elicited an increase in CBF which could be explained on the basis of an increase in perfusion pressure plus a decrease in CVR resulting from the increased metabolic demand secondary to the increase in heart rate. There was no evidence of a significant neural component directly affecting CVR, even in the presence of beta-adrenergic blockade.