The sensitivities of serum bile acid assays and some conventional liver function tests were studied in the early diagnosis and follow-up of intrahepatic cholestasis of pregnancy using 30 healthy pregnant women and 45 patients with intrahepatic cholestasis of pregnancy. Primary (cholic acid [CA] and chenodeoxycholic acid [CDCA]) and one secondary (deoxycholic acid [DCA]) bile acid were analyzed by radioimmunoassays and transaminases (SGPT and SGOT), alkaline phosphatase (AP), gamma-glutamyltranspeptidase (r-GT), and total and direct bilirubin were measured from the 16th to the 20th week of pregnancy until 35 to 60 days postpartum. When the first pathologic CA value appeared in the group of eight patients followed up before symptoms, in every case the CA:CDCA ratio was over one; there were mild itching symptoms in four cases, pathologically increased SGPT in four cases, elevated CDCA, AP, and r-GT levels in three cases, and elevated SGOT values in one case. Total and direct bilirubin concentrations were normal in all cases. Of all the analyses of the intrahepatic cholestasis of pregnancy patients (N=45) before delivery, CA was over the normal reference limit in 71%, CDCA in 57%, SGPT in 65%, SGOT in 59%, AP in 46%, r-GT in 35%, total bilirubin in 17%, and direct bilirubin in 38%. The correlation coefficients were significant (P<.001) between the primary bile acids and SGPT, SGOT, AP, and total and direct bilirubins. In the early diagnosis and follow-up of IHC of pregnancy the most sensitive indicators are: an increased CA level, a CA:CDCA ratio over 1, and an increase in SGPT activity.