In the present study particle-induced X-ray emission (PIXE) was used to analyse the spatial distribution of Ca2+ in aortic tissue of spontaneously hypertensive rats (SHR) and normotensive controls aged 1 week, 4 weeks and 12 weeks. Ca2+ was not elevated in the aortic smooth muscle of SHR aged 1 week (n = 9) compared with normotensive controls (n = 8; 186.8 +/- 89.9 micrograms Ca2+/g tissue). Ca2+ was significantly increased in the aortic smooth muscle of SHR aged 4 weeks (n = 9) compared with 4-week-old Wistar-Kyoto (WKY) rats (n = 12; 726.0 +/- 130.4 micrograms Ca2+/g tissue versus 440.3 +/- 214.4 micrograms Ca2+/g tissue) and in SHR aged 3 months (n = 15) compared with WKY (n = 12), (3317.0 +/- 734.0 tissue versus 1632.0 +/- 569.6 micrograms Ca2+/g tissue, respectively). The results confirm an age-related increase in arterial Ca2+ in normotensive rats and demonstrate that this age-related rise is accelerated in SHR.