A link between plasma calcium, dietary cations, and blood pressure has been suspected for some time, with human, experimental animal, and epidemiological data adduced to support this hypothesis. We identified 21 patients receiving regular maintenance hemodialysis, but not receiving any regular antihypertensive treatment, who had undergone 22 surgical removals of the parathyroid glands in the period 1978 to 1992. These patients' records were then scrutinized. The group preparathyroidectomy mean systolic blood pressure (BP) was 142.6 +/- 19.4 mm Hg. After the operation, the mean systolic BP was 133.6 +/- 21.9 mm Hg (P = 0.004). Plasma calcium decreased from 2.72 +/- 0.18 mmol/L to 2.52 +/- 0.19 mmol/L (P < 0.001). There was a correlation between the decreases in systolic blood pressure (SBP) (9.4%) and plasma calcium (7.3%); r = 0.60, P = 0.012. The decrease in SBP was not immediate, but delayed some months and complete by approximately 9 months after the operation. Furthermore, using ambulatory BP monitoring in a group of long-term hemodialysis patients, we found that parathyroidectomized patients had lower BP and pulse rates than those with intact parathyroid glands (SBP, 122.9 +/- 16.3 mm Hg v 102.9 +/- 9.9 mm Hg; pulse rates, 87.5 +/- 12.7 v 72.0 +/- 7.5 beats/min, P < .001, nonparathyroidectomy v postparathyroidectomy, both comparisons). These data support a link between plasma calcium and BP in patients receiving maintenance hemodialysis.