The part played by calcium in genesis of essential hypertension may be suspected. Yet, the whole of epidemiological research as well in the animal as in man is still not very convincing. The objective of such a research has been to appreciate the calcium intestinal absorption before and after nicardipine treatment in 11 subjects (5 M/6 F) aged between 32 and 82. The group is made up of 7 hypertensive patients (2 M/5 F) and 4 normotensive ones (3 M/1 F). Subjects showing bone disease, kidney insufficiency and stone in kidneys or under such a treatment as to interfere with calcium metabolism had been excluded. Dosage of calcium and phosphate, Na, K, aldosterone, in blood and urine and PTH and PRA in blood had been effectuated. Estimation of true calcium absorption has been made by double isotope deconvolution method. Blood pressure has been measured by semi-ambulatory monitoring method. Similar evaluation has been made after four weeks treatment (60 mg of nicardipine a day). Without any treatment, normotensive subjects have a lower intestinal absorption coefficient than the hypertensive ones, which is normal (non significative statistical results: NS). Under nicardipine, hypertensive patients seem to get lower intestinal absorption (NS); other clinical, biological parameters show no change, except a rise of apoprotein A after nicardipine treatment (P less than or equal to 0.05). So, the intestinal absorption of calcium would become higher in hypertensive subjects and diminished by calcium antagonist treatment.