In about 100 pregnant women in Okayama city, serum folate, vitamin B(12), iron levels and peripheral blood counts were estimated in each stages of pregnancy (16, 28, 36th weeks and 4 weeks after delivery). In most women, low serum iron levels were commonly observed in the late stages of pregnancy. The peripheral blood showed signs of iron deficiency. Mean serum folate level fell gradually as pregnancy came near to term. Macrocytic anemia was not observed and signs of folate deficiency were thought to be completely masked by that of iron deficiency. Hematological changes and serum iron, vitamin B(12) and folate levels after administration of iron plus folic acid were compared with changes and levels after supplement of iron alone in 100 pregnant women. No hematological benefits by adding folic acid was revealed. It is concluded that folic acid deficiency in pregnant Japanese women is mild and routine supplementation of folic acid is not required except proved cases of folic acid deficiency.