Using routine liver function tests, cholestasis of pregnancy was diagnosed in 86 pregnant women with pruritus. Serum aminotransferase levels were elevated in all cases, ASAT in 99%, and ALAT in 100%. In these patients serum concentrations of cholic, chenodeoxycholic, and deoxycholic acid were determined using a gas chromatographic method and were compared with those in a group of 40 uncomplicated pregnancies. Of these bile acids, cholic acid levels were most frequently elevated, ie, in 92% of the patients. The frequency of elevation of serum levels of alkaline phosphatase, and total and conjugated bilirubin was lower. Thus, it appears that in addition to serum aminotransferase levels the serum cholic acid concentration is a sensitive indicator of cholestasis of pregnancy. The cholestasis series was divided into 3 subgroups of increasing severity of cholestasis as assessed by maternal serum cholic acid levels, and the occurrence of signs of fetal distress was compared between these subgroups. The only intrauterine fetal loss in the series belonged to the severe cholestasis group. The incidence of meconium-stained amniotic fluid also increased significantly in this group, and 21 of the 24 cases with other signs of fetal distress were in the groups of moderate and severe cholestasis.