There was no significant difference in the tissue calcium content between spontaneously hypertensive rat (SHR) and normotensive rat aortae. <sup>45</sup>Ca uptake was significantly greater, whereas <sup>45</sup>Ca influx was significantly less in SHR than in control aortae. There was no difference in <sup>45</sup>Ca efflux in SHR and control tissues. <sup>45</sup>Ca influx in both SHR and control tissues was increased by potassium, not increased by norepinephrine and inhibited by Co<sup>:+</sup>, Mn<sup>++</sup> and La<sup>+++</sup> (all 0.5 mM). Both SHR and control aortae were equally inhibited by Mn<sup>++</sup> and Co<sup>++</sup> (0.1 mM). There was no difference in the <sup>45</sup>Ca uptake by microsome fraction from both SHR and control tissue. These data indicate some differences in the translocation of Ca<sup>++</sup> at the cellular level in SHR and control aortae.