The prevalence of intrahepatic cholestasis of pregnancy was studied immediately postpartum in 869 women from three distant Chilean cities differing in climate and food supply. Cholestatic jaundice of pregnancy was detected in 2.4% and pruritus gravidarum in 13.2%, without significant differences between the three cities. Every woman was then ethnically classified as predominantly Caucasoid, Araucanian Indian, or Aimara Indian. A significantly higher prevalence of cholestatic jaundice of pregnancy (5.5%) and pruritus gravidarum (22.1%) was found in Araucanians than in Caucasoids (2.5% and 12.6% respectively) or in the Aimaras (0 and 11.8% respectively). The prevalence of intrahepatic cholestasis of pregnancy in Araucanians increased directly with the degree of "ethnic purity." Recurrence of the disease in multiparous women was also greater in Araucanians (13.8%) than in Caucasoids (5.5%) or in the Aimaras (3.9%). We propose that an ethnic predisposition to develop intrahepatic cholestasis of pregnancy is present in Araucanian women and that the high prevalence of the disease in Chile is mainly influenced by ethnic admixture with this South American Indian (ethnic) group.