The systemic blood pressure and local blood flow to various organs are critically determined by the momentarily changing tone of small arteries and arterioles, in which sustained Ca²⁺ influx activated by a variety of mechanisms plays a central regulatory role. Recent progress in molecular biological research has unraveled unexpectedly diverse and complex aspects of Ca²⁺ entry channel molecules involved in this Ca²⁺ influx. These include, in addition to voltage-gated Ca²⁺ channels, several members of a newly emerging non-voltage-gated Ca²⁺ entry channel superfamily, the transient receptor potential (TRP) proteins, such as TRPC1, TRPC4, TRPC6, TRPV1, TRPV2, TRPV4, TRPM4 and polycystins (TRPPs). Neither of these channels exhibits simple properties to fulfill a single particular role, because they are multimodally activated or modulated in amazingly diverse ways by receptor stimulation, temperature, mechanical stress or lipid second messengers generated from various sources, and may interact mutually. There is good evidence to believe that many of these channels play non-trivial roles in both acute vasomotor control and long-term vascular remodeling. It seems that, amongst them, of central physiological importance is the TRPC6 isoform, since it is the most widely distributed isoform in the vasculature and has been shown to serve as an integrative Ca²⁺ signaling molecule for sympathetic nerve activity, vasopressor hormones and increased intravascular pressure. Here, we will focus on the TRPC6 channel and highlight especially its novel regulatory mechanism by 20-hydroxyeicosatetraenoic acid (20-HETE), in an intriguing connection with a reflex constriction of small arteries induced by pressurization referred to as the ‘myogenic response’. Muscarinic stimulation with 100μM carbachol (CCh) in murine TRPC6-overexpressing HEK293 cells evoked a large cationic current (I_TRPC6). Exposure to hypotonic external solution (-90mOsm; HTS) of these cells produced a rapid and reversible increase in the amplitude of I_TRPC6, and concomitantly elevated the intracellular Ca²⁺ concentration ([Ca²⁺]_i) or increased the rate of Ba²⁺ entry as evaluated by digital imaging microscopy. The potentiating effect of HTS on I_TRPC6 was unaffected when intracellular Ca²⁺ was strongly buffered by inclusion of 10mM BAPTA/4Ca²⁺ in the patch pipette, or when I_TRPC6 was more directly activated by internal perfusion with GTPγS (100μM) thus bypassing the receptor. However, 30min pretreatment with a 20-HETE production blocker HET0016 (3-10μM), which more selectively inhibits ω-hydroxylase than expoxygenase of non-hepatic vascular cytochrome P450, almost completely abolished the potentiating effect of HTS on I_TRPC6 or Ba²⁺ entry evoked by CCh. Increasing the intraluminal pressure (≥20 mm Hg) of cannulated rat mesenteric arteries (RMA; 2nd or 3rd branches) itself elicited a weak pressure-dependent reflex vasoconstriction dependent on extracellular Ca²⁺, but its extent was remarkably enhanced during α1-adrenergic receptor stimulation with low concentrations of phenylephrine (0.05-1.0μM). Pretreatment with HET0016 (10μM) greatly attenuated this reflex vasoconstriction, to an extent similar to that observed with Ca²⁺ elimination. These results collectively suggest that, at least in larger branches of RMA, 20-HETE production is a key intervening process for the development of myogenic tone at weak sympathetic excitation, in response to increased intravascular pressure. The mechanism underlying most likely involves 20-HETE-mediated potentiation of receptor-activated TRPC6 channels.