The transient receptor potential melastatin 8 (TRPM8) channel has been characterized as a cold and menthol receptor expressed in a subpopulation of sensory neurons, but was recently identified in other tissues, including respiratory tract, urinary system, and vasculature. Thus, TRPM8 may play multiple functional roles, likely to be in a tissue- and activation state-dependent manner. We examined TRPM8 channel presence in large arteries from rats and functional consequences of their activation. We also aimed to examine whether these channels contribute to control of conscious human skin blood flow. TRPM8 mRNA and protein were detected in rat tail, femoral and mesenteric arteries and thoracic aorta. This was confirmed in single isolated vascular myocytes by immunocytochemistry. Isometric contraction studies on endothelium-denuded relaxed rat vessels found small contractions on application of TRPM8-specific agonist, menthol (300µM). However, both menthol and another agonist, icilin (50µM) caused relaxation of vessels pre-contracted with KCl (60mM) or -adrenoceptor agonist, phenylephrine (2µM), and a reduction in sympathetic nerve-mediated contraction. These effects were antagonized by bromoenol lactone treatment suggesting involvement of iPLA₂ activation in TRPM8-mediated vasodilatation. In thoracic aorta with intact endothelium, menthol-induced inhibition of KCl-induced contraction was enhanced. This was unaltered by pre-incubation with either N-nitro-l-arginine methyl ester (L-NAME, 100nM), a nitric oxide synthase inhibitor, or acetylcholine receptor antagonist, atropine (1µM). Application of menthol (3% solution, topical application) to skin caused increased blood flow in conscious humans, measured by laser Doppler fluximetry. Vasodilatation was markedly reduced or abolished by prior application of L-NAME (passive application, 10mM) or atropine (iontophoretic application, 100nM, 30 sec @ 70µA). We conclude that TRPM8 channels are present on rat artery vascular smooth muscle and on activation cause vasoconstriction or vasodilatation, dependent on previous vasomotor tone. TRPM8 channels may also contribute to human cutaneous vasculature control, likely with the involvement of additional neuronal mechanisms.