The sympathetic nervous system (SNS) plays an essential role in the control of total peripheral vascular resistance by controlling the contraction of small arteries. The SNS also exerts long‐term trophic influences in health and disease; SNS hyperactivity accompanies most forms of human essential hypertension, obesity and heart failure. At their junctions with smooth muscle cells, the peri‐arterial sympathetic nerves release ATP, noradrenaline (NA) and neuropeptide Y (NPY) onto smooth muscle cells. Confocal Ca²⁺ imaging studies reveal that ATP and NA each produce unique types of postjunctional Ca²⁺ signals and consequent smooth muscle cell contractions. Neurally released ATP activates postjunctional P2X₁ receptors to produce local, non‐propagating Ca²⁺ transients, termed ‘junctional Ca²⁺ transients’, or ‘jCaTs’. Neurally released NA binds to α₁‐adrenoceptors and can activate Ca²⁺ waves or more uniform global changes in [Ca²⁺]. Neurally released NPY does not appear to produce Ca²⁺ transients directly, but significantly modulates NA‐induced Ca²⁺ signalling. The neural release of ATP and NA, as judged by postjunctional Ca²⁺ signals, electrical recording of excitatory junction potentials and carbon fibre amperometry to measure NA, varies markedly with the pattern of nerve activity. This probably reflects both pre‐ and postjunctional mechanisms, which are not yet fully understood. These phenomena, together with different temporal patterns of sympathetic nerve activity in different regional circulations, are probably an important mechanistic basis of the important selective regulation of regional vascular resistance and blood flow by the sympathetic nervous system.