Brain natriuretic peptide (BNP) was increased in many hypertensive subjects. In this study, we have evaluated maternal, umbilical plasma and amniotic fluid BNP and atrial natriuretic peptide (ANP) in 19 normotensive pregnant women and in 35 preeclamptic patients. The maternal plasma and umbilical cord plasma ANP (p < 0.05) and BNP (p < 0.005) levels were significantly higher than those in normal pregnancy. There was no significant correlation among ANP level, BNP level, clinical symptoms and laboratory examinations. It is suggested that ANP and BNP may be rather a sequel to preeclamptic pathophysiological changes, and may not play an important role as the etiological factor of preeclampsia.