Homocysteine is associated with endothelial dysfunction and cardiovascular disease, and elevated concentrations of homocysteine have been found in preeclampsia. The purpose of this study was to investigate maternal and fetal concentrations of total homocysteine and related metabolites (including cysteine, choline, and betaine), and possible associations with infant birth weight. Women with preeclampsia (n=47) and controls (n=51), who underwent cesarean section, were included. Maternal plasma, umbilical vein, and artery plasma were analyzed. Median concentrations of homocysteine, cysteine, choline, and betaine were significantly higher in women with preeclampsia than controls, both in maternal and fetal plasma. There were no differences in folate and vitamin B12 concentrations between the groups, neither for maternal nor fetal samples. Maternal homocysteine concentration was a negative predictor for birth weight only in the preeclampsia group. Elevated homocysteine and cysteine concentration in maternal circulation in preeclampsia is reflected in the fetal circulation. The clinical significance of elevated homocysteine and cysteine concentrations in maternal and fetal compartments in preeclampsia remain to be explored, both regarding fetal growth and development of disease later in life.