To assess the effect of aluminium on the calcium-sensing receptor expression, proliferation, and apoptosis in parathyroid glands from rats with chronic renal failure, 2(1/2)-month-old male Wistar rats were 7/8 nephrectomized. Eight weeks after surgery the rats were divided into two groups, one receiving intraperitoneal AlCl3 for 8 weeks and the other receiving intraperitoneal placebo. Serum Al, Ca, P, creatinine, and PTH were measured. Parathyroid glands were removed, formaldehyde-fixed, and paraffin-embedded. Calcium-sensing receptor and proliferation were detected by immunohistochemistry and apoptosis by TUNEL and propidium iodide uptake. At the end of the study, despite higher levels of serum P in the aluminium group (6.27 +/- 0.63 vs. 5.56 +/- 0.58 mg/dL; P = 0.045), serum PTH was lower (89.6 +/- 57.7 vs. 183.1 +/- 123.8 pg/mL; P = 0.059). No significant differences were found in the calcium-sensing receptor expression between groups (aluminium: 27.1 +/- 7.6; placebo: 25.4 +/- 3.5 RU). Rats receiving aluminium showed a significantly lower cell proliferation rate than the control rats (0.54 +/- 0.69 vs. 4.43 +/- 3.10 cells/mm2; P = 0.003). No apoptotic events were detected. Aluminium was able to reduce the cell proliferation of the parathyroid glands. Due to the low apoptosis rate, however, it was not possible to find any change. Aluminium had no effect on the calcium-sensing receptor expression.