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