The effect of varying the dietary intake of Na, K, Ca, Mg, Cd and Pb on blood pressure in 16 groups of rats (10 rats each group) weighing 200 g initially was studied. The animals received Na, K, Ca, and Mg in amounts calculated to be 20% above or 20% below the normal intake of these elements. Lead was given as PbCl2 (300 mg/l) in the drinking water and Cd was given in the drinking water in a concentration of 5 mg Cd/l. The animals were on the diets for 16 weeks. The diets were sufficient for growth and maintenance as indicated by weight increases of 35-45% during the 16-week period. Eight Cd-ingesting groups exhibited increases in blood pressure of from 2 to 12%. The blood pressure of 8 groups of rats which received high levels of Ca and Mg but no Cd exhibited decreases in blood pressure of from 4 to 11%. The other elements modified these responses. The level to which blood pressure would rise or fall could not be predicted on the presence or absence of one mineral alone. These data support the concept that alterations in dietary mineral intake affect the blood pressure.