Appropriate release of nitric oxide (NO) is critical for normal physiological functioning of the cardiovascular system. Although a rise in intracellular Ca2+ concentration ([Ca2+]i) in endothelial cells (ECs) is thought to play an important role in the coordination of NO release, the molecular mechanism underlying this influx is poorly understood. The work presented here outlines the molecular mechanisms responsible for regulating endothelial [Ca2+]i and its implication to NO production and release, and involved two major areas of study. Firstly, we identified the presence of a signaling complex comprised of stromal interaction molecule 1 (STIM1), transient receptor potential protein (canonical subtype) 1 (TRPC1), and the Na+/Ca2+ exchanger 1 (NCX1) in cultured ECs, which may be an important component of the Ca2+ influx pathway necessary for the activation of endothelial NO synthase (eNOS) during agonist stimulation. Secondly, recruitment of the NCX in reverse mode was shown to play an important role in flow-mediated dilation and the corresponding phosphorylation of serine-1177 of eNOS (S1177-eNOS). This is the first study to identify S1177-eNOS phosphorylation in response to flow in small (< 300 μm), pressurized, myogenic rat cerebral arteries. These findings are significant because the potential involvement of a TRP-NCX signaling complex in ECs has been an unresolved issue for some time. Therefore the work of this thesis provides unique insight into the molecular mechanisms that contribute to the regulation of endothelial [Ca2+]i.