We have undertaken studies in humans and animals that aimed to obtain further information about the intake and excretion of boron (B) as well as its effects on markers of coronary heart disease. In humans, we have shown that the intake of B is 2.2 mg/d; its urinary excretion is 1.9 mg/d, and there appears to be little intraindividual variation. Supplementation with 10 mg of B/d resulted in the recovery of 84% of the dose in the urine and a significant increase in plasma estradiol concentration, but no effect on plasma lipoproteins. In rats, increasing the intake of B through the drinking water is reflected in the tissue concentrations, results in an increase in plasma testosterone and vitamin D, and results in a decrease in HDL cholesterol. It is clear that B has the potential to impact significantly on a number of metabolic processes.