Minerals in serum and erythrocyte were measured in 30 normal non-pregnant women, 156 normal pregnant women and 84 normal postpartum women, The mineral changes during pregnancy were observed monthly from the 4th month of gestation on. In the postpsrtum the values of finerals were measured on the second postpartum day. The results were as follows: 1) The mean value of serum calcium in non-pregnant women was 4.74 0.20mEq/L. The changes during pregnancy revealed slight fall and the peak appeared in the 7th to 8th month. The mean value of the postpartum was lower than that of non-pregnant. 2) The mean value of serum magnesium in non-pregant women was 1.98 0.12mEq/L. The changes during pregnancy revealed slight fall and the lowest value appeared in the 8th month. The mean value of the postpartum rose up but was lower than that of non-pregnant. The mean value of erythrocyte in non-pregnant women was 7.37 0.54mEq/L. The changes during pregnancy revealed higher than that of non-pregnant. The peak appeared in the 7th month. The mean value of the postpartum returned back to non-pregnant level. 3) The mean value of serum phosphorus in non-pregnant women was 3.97 1.05mg/100ml. The changes during pregnancy revealed lower than non-pregnant value and the lowest value appeared in the 7th month. The mean value of the postpartum rose up. 4) The mean value of serum sodium in non-pregnant women was 138.27 2.58mEq/L. The changes during prgnancy revealed lower than non-pregnant value and the peak appeared in the 7th month. The mean value of the postpartum returned back to non-pregnant level. The mean value of erythrocyte sodium in non-pregnant women was 12.48 3.40mEq/L. The value of the 2nd trimester of pregnancy fell but it was rising in the 3rd trimester up above the non-pregnant level. The peak appeared in the 9th month. The mean value of the postpartum remained very high steadily. 5) The mean value of serum potassium in non-pregnant women was 4.21 0.41mEq/L. The changes during pregnancy revealed fall and the peak appeared in the 7th month. The mean value of the postpartum did not return back to non-pregnant level. The mean value of erythrocyte potassium in non-pregnant women was 96.96 4.33mEq/L. The changes during pregnancy revealed higher than non-pregnant value and the peak appeared in the 8th month. The mean value of the postpartum was higher than non-pregnant level. 6) The mean value of serum chloride in non-pregnant women was 107.10 3.04mEq/L. The changes during pregnancy revealed slight fall and the peak appeared in the 8th month. The mean value of the postpartum returned back to non-pregnant level. The mean value of erythrocyte chloride in non-pregnant women was 37.17 8.38mEq/L. The changes during pregnancy revealed fall and the peak appeared in the 6th month. The mean value of the postpartum returned back almost to non-pregnant level. 7) The mean value of serum iron in non-pregnant women was 108.10 33.40㎍/100ml. The value in the 4th month gestation revealed rather higher than that of non-pregnant and then fell gradually. Meantime, momentary rising appeared in the 6th month. The mean value of the postpartum was about half of non-pregnant level.