Pregnancy induced hypertension is multifaceted syndrome with variable involvement of several key organ systems, so sensitive and specific laboratory tests for predicting severity and prognosis, and early diagnosis of this disease are required. Because heme catabolism results in equimolar production of carboxyhemoglobin, iron and bilirubin, a concomittant rise of these parameters would provide confirmation of increased heme catabolism. Microangiopathic hemolytic anemia may occurs in severe preeclampsia, but it is not known whether increased red cell turnover occurs with mild preeclampsia as complication. The purpose of this study was to confirm that increased heme catabolism also occurs in patients with mild preeclampsia. The analysis of data was done on 23 cases with mild preeclampsia and 35 normal pregnant women, who were admitted to Yeungnam University Hospital from October 1992 to March 1993. The results were as follows. 1. The mean antepartum serum iron concentration was significantly higher in the group with mild preeclampsia($86.5{pm}6.1{mu}g/dl$) than in the controls($53.2{pm}5.3{mu}g/dl$). 2. The mean antepartum and postpartum carboxyhemoglobin concentrations were significantly higher in the group with mild preeclampsia(antepartum : $2.55{pm}0.42{mu}g/dl$, postpartum : $1.21{pm}0.4{mu}g/dl$) than the controls(antepartum : $0.61{pm}0.2{mu}g/dl$, postpartum $0.53{pm}0.2{mu}g/dl$) 3. During postpartum, carboxyhemoglobin concentration in preeclampsia reduced significantly from antepartum level, but, there was no difference between antepartum and postpartum carboxyhemoglobin concentrations among controls. 4. Bilirubin concentrations were similar in both groups.